Generate contract types, pin fixtures to spec, add build and ADRs

Completes FLUID-WP-0002. The record types in internal/contract are
generated from schemas/ by a dependency-free generator; fixtures
transcribed from the spec's worked examples validate against those
schemas and round-trip through the generated types with
DisallowUnknownFields, so a spec change that misses the schemas fails
CI rather than drifting silently.

Adds identifier prefix helpers, Makefile, GitHub Actions, and five ADRs
recording the Go choice, out-of-process attachment, the wire contract as
boundary, the evidence store, and revision identity.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014KmVxhJ35tCo7rE7UnLwWu

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1116572@bnt-lap001
Assistant-Session: 8ba9bb93-a72a-4883-b189-2499cce5c400

conformance/fixtures/json/revision.json

@@ -0,0 +1,150 @@
+{
+  "fluid_revision": {
+    "adaptation_classes": [
+      "contract"
+    ],
+    "adoption": {
+      "active_consumers": 119,
+      "adoption_rate": 0.289,
+      "eligible_consumers": 412,
+      "retained_adoption_rate": null
+    },
+    "audit": {
+      "immutable_event_refs": [
+        "EV-990221",
+        "EV-990244",
+        "EV-990281"
+      ]
+    },
+    "backend_requirements": [],
+    "compatibility": {
+      "breaking_changes": [],
+      "class": "BACKWARD_COMPATIBLE",
+      "compatibility_evidence_refs": [
+        "test:compat-suite-775"
+      ],
+      "deprecations": [],
+      "supersedes": []
+    },
+    "complexity": {
+      "after": {
+        "operation_count": 40,
+        "surface_area": 42
+      },
+      "before": {
+        "operation_count": 39,
+        "surface_area": 41
+      },
+      "budget_status": "WITHIN_BUDGET",
+      "delta_score": 0.18
+    },
+    "contract": {
+      "artifact_ref": "artifact:openapi/customer-finance-api/r22",
+      "digest": "sha256:3b1f9c2e7a4d8b6051e2c9f0a7d4b83e15c6f2a9d0b7e4c1836a5f2d9c0b7e41",
+      "type": "openapi",
+      "version": "3.1"
+    },
+    "created_at": "2026-09-04T13:10:00Z",
+    "created_by": {
+      "id": "fluid-daimon/customer-finance-api",
+      "type": "daimon"
+    },
+    "deployment": {
+      "current_exposure": {
+        "cohorts": [
+          "partner-integrations",
+          "coding-agents"
+        ],
+        "traffic_share": 0.28
+      },
+      "environments": [
+        {
+          "name": "production",
+          "routing_policy_ref": "route-policy:rp-118",
+          "started_at": "2026-09-05T08:00:00Z"
+        }
+      ]
+    },
+    "economics": {
+      "build_cost": 38.2,
+      "currency": "EUR",
+      "experiment_cost_to_date": 12.4
+    },
+    "fitness": {
+      "baseline_revision": "R-000220",
+      "measurement_window": {
+        "end": null,
+        "start": "2026-09-05T08:00:00Z"
+      },
+      "metrics": {
+        "error_rate": {
+          "baseline": 0.008,
+          "current": 0.007
+        },
+        "p95_latency_ms": {
+          "baseline": 300,
+          "current": 302,
+          "guardrail": 315
+        },
+        "requests_per_completed_task": {
+          "baseline": 2.7,
+          "current": 1.15,
+          "target": 1.2
+        }
+      }
+    },
+    "id": "R-000221",
+    "implementation": {
+      "artifact_ref": "artifact:adapter/customer-finance-api/r22",
+      "build_ref": "build:8871",
+      "digest": "sha256:3b1f9c2e7a4d8b6051e2c9f0a7d4b83e15c6f2a9d0b7e4c1836a5f2d9c0b7e41",
+      "source_ref": "git:9f4c2ab"
+    },
+    "interface_evolution_intent": {
+      "artifact_ref": "artifact:intent/customer-finance-api/IEI-7",
+      "version": "IEI-7"
+    },
+    "interface_id": "customer-finance-api",
+    "originating_hypotheses": [
+      "H-000184"
+    ],
+    "parent_revision": "R-000220",
+    "promotion": {
+      "authorized_at": null,
+      "authorized_by": null,
+      "eligible": true,
+      "recommendation_reason": "Target fitness reached with no guardrail violations.\n",
+      "recommended_state": "STABLE"
+    },
+    "provenance": {
+      "decision_refs": [
+        "D-2811"
+      ],
+      "experiment_refs": [
+        "E-000093"
+      ],
+      "telemetry_refs": [
+        "telemetry:invoice-pattern-2026w36"
+      ]
+    },
+    "revision_number": 22,
+    "rollback": {
+      "procedure_ref": "runbook:rollback-r22",
+      "supported": true,
+      "target_revision": "R-000220"
+    },
+    "schema_version": "0.1",
+    "state": "CANDIDATE",
+    "verification": {
+      "policy_check": "PASSED",
+      "security_check": "PASSED",
+      "status": "PASSED",
+      "test_refs": [
+        "test:unit-12081",
+        "test:contract-8821",
+        "test:security-610",
+        "test:compat-suite-775"
+      ]
+    }
+  }
+}