Extract binder package from citation-evidence (EBIND-WP-0001)

Extracts citation-evidence/src/binder/ into this repo as the standalone
@citation-evidence/evidence-binder package: headless binding service +
in-memory link repo, active-state machine, the SharedContracts §7
rect-registry contract (registry, change pumps, hooks, SVG overlay), and
the target-neutral reference FormRenderer.

- toolchain mirrors sibling extracted repos (pnpm/tsc/vitest/eslint);
  imports rewritten from @shared/@engine aliases to the engine's
  @citation-evidence/engine package specifiers
- dependency boundary (engine + anchor only; no source/work/umbrella)
  enforced via eslint no-restricted-imports
- docs: extraction inventory + contract deltas, ADR-0001 (reference UI
  kept as supported exports), refreshed README/SCOPE/INTENT, populated
  capabilities index
- typecheck + lint green, 37 tests passing

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/services/bindings.test.ts

@@ -0,0 +1,180 @@
+/**
+ * Binding service + in-memory link repo tests.
+ *
+ * Exercises every public surface plus the §4 events the service emits.
+ */
+
+import { describe, expect, it } from "vitest";
+
+import type {
+  EvidenceLink,
+  EvidenceTarget,
+} from "@citation-evidence/engine/shared";
+import type {
+  EvidenceItemId,
+  EvidenceLinkId,
+} from "@citation-evidence/engine/shared";
+
+import { createEventBus } from "@citation-evidence/engine";
+import type { EngineEvent } from "@citation-evidence/engine";
+
+import { createInMemoryLinkRepo } from "../repos/in-memory-links";
+import { createBindingService } from "./bindings";
+
+function makeFixture() {
+  const bus = createEventBus();
+  const repo = createInMemoryLinkRepo();
+  const events: EngineEvent[] = [];
+  bus.onAny((e) => events.push(e));
+  let counter = 0;
+  const now = () => `2026-05-25T00:00:0${counter++}.000Z`;
+  const service = createBindingService(repo, bus, now);
+  return { bus, repo, events, service };
+}
+
+const FIELD_A: EvidenceTarget = { targetType: "form-field", targetId: "summary" };
+const FIELD_B: EvidenceTarget = { targetType: "form-field", targetId: "amount" };
+const EV1 = "ev_test_one" as EvidenceItemId;
+const EV2 = "ev_test_two" as EvidenceItemId;
+
+describe("createBindingService", () => {
+  it("linkEvidenceToTarget creates a link, emits EvidenceLinkCreated, and persists it", () => {
+    const { service, repo, events } = makeFixture();
+
+    const link = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+    });
+
+    expect(link.evidenceItemId).toBe(EV1);
+    expect(link.targetType).toBe("form-field");
+    expect(link.targetId).toBe("summary");
+    expect(link.relation).toBe("supports");
+    expect(link.status).toBe("candidate");
+    expect(link.createdAt).toBe(link.updatedAt);
+
+    expect(repo.get(link.id)).toEqual(link);
+
+    const created = events.filter((e) => e.type === "EvidenceLinkCreated");
+    expect(created).toHaveLength(1);
+    expect(created[0]).toMatchObject({ linkId: link.id, link });
+  });
+
+  it("honours explicit relation/status/confidence", () => {
+    const { service } = makeFixture();
+
+    const link = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+      relation: "contradicts",
+      status: "conflicting",
+      confidence: 0.42,
+      createdBy: "tegwick",
+    });
+
+    expect(link.relation).toBe("contradicts");
+    expect(link.status).toBe("conflicting");
+    expect(link.confidence).toBe(0.42);
+    expect(link.createdBy).toBe("tegwick");
+  });
+
+  it("listEvidenceForTarget returns only links for the requested target", () => {
+    const { service } = makeFixture();
+    const a1 = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+    service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_B });
+    const a2 = service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_A });
+
+    const linksForA = service.listEvidenceForTarget(FIELD_A);
+    expect(linksForA.map((l) => l.id).sort()).toEqual([a1.id, a2.id].sort());
+  });
+
+  it("listTargetsForEvidence returns all targets an evidence item is linked to", () => {
+    const { service } = makeFixture();
+    const a = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+    const b = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_B });
+    service.linkEvidenceToTarget({ evidenceItemId: EV2, target: FIELD_A });
+
+    const targets = service.listTargetsForEvidence(EV1);
+    expect(targets.map((l) => l.id).sort()).toEqual([a.id, b.id].sort());
+  });
+
+  it("unlinkEvidence removes the link and reports success/failure", () => {
+    const { service } = makeFixture();
+    const link = service.linkEvidenceToTarget({ evidenceItemId: EV1, target: FIELD_A });
+
+    expect(service.unlinkEvidence(link.id)).toBe(true);
+    expect(service.getLink(link.id)).toBeNull();
+    expect(service.unlinkEvidence(link.id)).toBe(false);
+    expect(service.unlinkEvidence("evlink_unknown" as EvidenceLinkId)).toBe(false);
+  });
+
+  it("updateLink merges patch, bumps updatedAt, and emits EvidenceLinkUpdated", () => {
+    const { service, events } = makeFixture();
+    const original = service.linkEvidenceToTarget({
+      evidenceItemId: EV1,
+      target: FIELD_A,
+    });
+
+    const updated = service.updateLink(original.id, {
+      status: "confirmed",
+      confidence: 0.9,
+    });
+
+    expect(updated.status).toBe("confirmed");
+    expect(updated.confidence).toBe(0.9);
+    expect(updated.relation).toBe(original.relation);
+    expect(updated.updatedAt).not.toBe(original.updatedAt);
+
+    const updatedEvents = events.filter((e) => e.type === "EvidenceLinkUpdated");
+    expect(updatedEvents).toHaveLength(1);
+    expect((updatedEvents[0] as Extract<EngineEvent, { type: "EvidenceLinkUpdated" }>).link).toEqual(updated);
+  });
+
+  it("updateLink throws on unknown id", () => {
+    const { service } = makeFixture();
+    expect(() =>
+      service.updateLink("evlink_unknown" as EvidenceLinkId, { status: "verified" }),
+    ).toThrow(/unknown id/);
+  });
+
+  it("setActiveEvidence emits EvidenceItemActivated with source=form-field", () => {
+    const { service, events } = makeFixture();
+    service.setActiveEvidence(EV1);
+    const activated = events.filter((e) => e.type === "EvidenceItemActivated");
+    expect(activated).toHaveLength(1);
+    expect(activated[0]).toMatchObject({ evidenceItemId: EV1, source: "form-field" });
+  });
+});
+
+describe("EvidenceLinkRepository (in-memory)", () => {
+  it("rejects duplicate ids on create", () => {
+    const repo = createInMemoryLinkRepo();
+    const link: EvidenceLink = {
+      id: "evlink_x" as EvidenceLinkId,
+      evidenceItemId: EV1,
+      targetType: "form-field",
+      targetId: "f",
+      relation: "supports",
+      status: "candidate",
+      createdAt: "2026-05-25T00:00:00.000Z",
+      updatedAt: "2026-05-25T00:00:00.000Z",
+    };
+    repo.create(link);
+    expect(() => repo.create(link)).toThrow(/duplicate/);
+  });
+
+  it("update throws on unknown id", () => {
+    const repo = createInMemoryLinkRepo();
+    const link: EvidenceLink = {
+      id: "evlink_unknown" as EvidenceLinkId,
+      evidenceItemId: EV1,
+      targetType: "form-field",
+      targetId: "f",
+      relation: "supports",
+      status: "candidate",
+      createdAt: "2026-05-25T00:00:00.000Z",
+      updatedAt: "2026-05-25T00:00:00.000Z",
+    };
+    expect(() => repo.update(link)).toThrow(/unknown/);
+  });
+});

src/services/bindings.ts

@@ -0,0 +1,118 @@
+/**
+ * Binding service — links EvidenceItems to structured targets.
+ *
+ * Implements `wiki/ArchitectureOverview.md` §4.6 + SharedContracts §2.4
+ * (status enum), §2.5 (relation enum). Emits §4 events:
+ * `EvidenceLinkCreated`, `EvidenceLinkUpdated`, `EvidenceItemActivated`.
+ *
+ * MVP semantics:
+ *   - `linkEvidenceToTarget` defaults `relation="supports"`, `status="candidate"`.
+ *   - `unlinkEvidence` is hard-delete; the rejected-status path is left to
+ *     a later ADR.
+ *   - `setActiveEvidence` emits an `EvidenceItemActivated` event with
+ *     `source="form-field"` so the viewer/sidebar can react.
+ */
+
+import type {
+  EvidenceLink,
+  EvidenceLinkStoredStatus,
+  EvidenceRelation,
+  EvidenceTarget,
+} from "@citation-evidence/engine/shared";
+import type { EvidenceItemId, EvidenceLinkId } from "@citation-evidence/engine/shared";
+import { newId } from "@citation-evidence/engine/shared";
+
+import type { EventBus } from "@citation-evidence/engine";
+
+import type { EvidenceLinkRepository } from "../repos/in-memory-links";
+
+export interface LinkEvidenceToTargetInput {
+  readonly evidenceItemId: EvidenceItemId;
+  readonly target: EvidenceTarget;
+  readonly relation?: EvidenceRelation;
+  readonly status?: EvidenceLinkStoredStatus;
+  readonly confidence?: number;
+  readonly createdBy?: string;
+}
+
+export interface UpdateLinkStatusInput {
+  readonly status?: EvidenceLinkStoredStatus;
+  readonly relation?: EvidenceRelation;
+  readonly confidence?: number;
+}
+
+export interface BindingService {
+  linkEvidenceToTarget(input: LinkEvidenceToTargetInput): EvidenceLink;
+  unlinkEvidence(id: EvidenceLinkId): boolean;
+  updateLink(id: EvidenceLinkId, input: UpdateLinkStatusInput): EvidenceLink;
+  getLink(id: EvidenceLinkId): EvidenceLink | null;
+  listEvidenceForTarget(target: EvidenceTarget): readonly EvidenceLink[];
+  listTargetsForEvidence(evidenceItemId: EvidenceItemId): readonly EvidenceLink[];
+  setActiveEvidence(evidenceItemId: EvidenceItemId): void;
+}
+
+export function createBindingService(
+  links: EvidenceLinkRepository,
+  bus: EventBus,
+  now: () => string = () => new Date().toISOString(),
+): BindingService {
+  return {
+    linkEvidenceToTarget(input) {
+      const ts = now();
+      const link: EvidenceLink = {
+        id: newId("evidence-link"),
+        evidenceItemId: input.evidenceItemId,
+        targetType: input.target.targetType,
+        targetId: input.target.targetId,
+        relation: input.relation ?? "supports",
+        status: input.status ?? "candidate",
+        ...(input.confidence !== undefined ? { confidence: input.confidence } : {}),
+        ...(input.createdBy !== undefined ? { createdBy: input.createdBy } : {}),
+        createdAt: ts,
+        updatedAt: ts,
+      };
+      const stored = links.create(link);
+      bus.emit({ type: "EvidenceLinkCreated", linkId: stored.id, link: stored });
+      return stored;
+    },
+    unlinkEvidence(id) {
+      const removed = links.delete(id);
+      if (removed) {
+        bus.emit({ type: "EvidenceLinkRemoved", linkId: id });
+      }
+      return removed;
+    },
+    updateLink(id, input) {
+      const existing = links.get(id);
+      if (!existing) {
+        throw new Error(`BindingService.updateLink: unknown id ${id}`);
+      }
+      const next: EvidenceLink = {
+        ...existing,
+        ...(input.status !== undefined ? { status: input.status } : {}),
+        ...(input.relation !== undefined ? { relation: input.relation } : {}),
+        ...(input.confidence !== undefined ? { confidence: input.confidence } : {}),
+        updatedAt: now(),
+      };
+      const stored = links.update(next);
+      bus.emit({ type: "EvidenceLinkUpdated", linkId: stored.id, link: stored });
+      return stored;
+    },
+    getLink(id) {
+      return links.get(id);
+    },
+    listEvidenceForTarget(target) {
+      return links.listForTarget(target);
+    },
+    listTargetsForEvidence(evidenceItemId) {
+      return links.listForEvidenceItem(evidenceItemId);
+    },
+    setActiveEvidence(evidenceItemId) {
+      bus.emit({
+        type: "EvidenceItemActivated",
+        evidenceItemId,
+        source: "form-field",
+      });
+    },
+  };
+}

src/services/index.ts

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+export * from "./bindings";