EANCH-WP-0001 T03: extract pure selector creation + resolution core

Move types.ts, selectors/{index,create,resolve}.ts, and pdf-selector-math.ts
out of citation-evidence/src/anchor/ into src/ (pdf math under src/pdf/).
Rewrite all @shared/* imports to @citation-evidence/engine/shared; wire the
public entrypoint (src/index.ts) and the ./pdf subpath. Port the three unit
suites. Confidence ladder and selector-redundancy rules preserved verbatim.

Verified: pnpm test (29 passed), typecheck, and lint all green.
Also adds Node/TS .gitignore entries and the pnpm lockfile.

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

src/types.ts

@@ -0,0 +1,97 @@
+/**
+ * Adapter-side types owned by `evidence-anchor`.
+ *
+ * Implements the contract surface from `wiki/SharedContracts.md` §5 and the
+ * resolution result shape from `wiki/ArchitectureOverview.md` §3.3 / §7.
+ *
+ * Anything that mentions a concrete viewer library (pdfjs, react-pdf-highlighter-plus)
+ * lives *behind* this surface, never on it. `src/shared/` and `src/engine/`
+ * must never import this file.
+ */
+
+import type { Document, DocumentRepresentation } from "@citation-evidence/engine/shared";
+import type { Selector } from "@citation-evidence/engine/shared";
+import type { AnnotationResolutionStatus } from "@citation-evidence/engine/shared";
+import type { NormalizedRect } from "@citation-evidence/engine/shared";
+
+/**
+ * The raw selection captured from a viewer adapter — an opaque payload that
+ * the adapter understands. The shape is intentionally permissive: each
+ * concrete adapter narrows the `kind` discriminator and adds its own
+ * payload. The shared layer never inspects the payload directly.
+ */
+export type SelectionCapture =
+  | PdfSelectionCapture
+  | DomSelectionCapture;
+
+export interface PdfSelectionCapture {
+  readonly kind: "pdf";
+  /** Verbatim selected text, before canonical normalisation. */
+  readonly text: string;
+  /** 1-indexed physical page number the selection started on. */
+  readonly page: number;
+  /** Page-relative normalized rectangles covering the selection (0..1). */
+  readonly rects: readonly NormalizedRect[];
+  /** Optional bounding rectangle (page-relative, normalized). */
+  readonly boundingRect?: NormalizedRect;
+}
+
+/** Reserved for the HTML/Markdown adapter. Not implementable in MVP. */
+export type DomSelectionCapture = never;
+
+/**
+ * A passage located inside a representation, ready to be scrolled to and
+ * highlighted.
+ */
+export interface ResolvedAnchorTarget {
+  readonly representationId: string;
+  /** 1-indexed page (PDF) or undefined for HTML/Markdown. */
+  readonly page?: number;
+  /** Page-relative normalized rectangles to highlight. */
+  readonly rects?: readonly NormalizedRect[];
+  /** Canonical-text offsets, when known. */
+  readonly textPosition?: { readonly start: number; readonly end: number };
+}
+
+/**
+ * The outcome of asking the adapter to resolve a `Selector[]`.
+ * Matches `wiki/ArchitectureOverview.md` §3.3.
+ */
+export interface AnchorResolution {
+  readonly status: AnnotationResolutionStatus;
+  /** 0..1 confidence in the best candidate. */
+  readonly confidence: number;
+  readonly candidates: readonly ResolvedAnchorTarget[];
+  /** Names of the selector kinds that produced a usable candidate. */
+  readonly usedSelectorTypes: readonly string[];
+  readonly warnings?: readonly string[];
+}
+
+export interface HighlightRenderOptions {
+  readonly color?: string;
+  readonly opacity?: number;
+}
+
+/**
+ * The format-neutral viewer adapter contract from `wiki/SharedContracts.md` §5.
+ *
+ * Concrete implementations live alongside the viewer they wrap (e.g. the
+ * PDF spike in `src/anchor/pdf-viewer-adapter-spike.tsx`). The shared/engine
+ * layers depend only on this interface.
+ */
+export interface DocumentViewerAdapter {
+  readonly mediaTypes: readonly string[];
+  load(document: Document, representation?: DocumentRepresentation): Promise<void>;
+  getCurrentSelection(): Promise<SelectionCapture | null>;
+  createSelectorsFromSelection(selection: SelectionCapture): Promise<Selector[]>;
+  resolveSelectors(selectors: readonly Selector[]): Promise<AnchorResolution>;
+  scrollToResolvedTarget(
+    target: ResolvedAnchorTarget,
+    opts?: { readonly center?: boolean; readonly behavior?: "auto" | "smooth" },
+  ): Promise<void>;
+  renderHighlight(
+    target: ResolvedAnchorTarget,
+    opts?: HighlightRenderOptions,
+  ): Promise<void>;
+  getHighlightClientRects(annotationId: string): Promise<readonly DOMRect[]>;
+}