Add game data capture vertical slice

tools/game-data-capture/contracts/README.md

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+# Game Data Capture Contracts
+
+RG-1 freezes contract version 1 for the taxonomy, workflow states, evidence model, archive manifest, and ISAC handoff boundary.
+
+## Files
+
+- `domain-contract-v1.json` lists every family/view pair, record type, Gear slot, abstention reason, state, and allowed transition.
+- `screenshot-classification.schema.json` validates one hierarchical screen classification.
+- `evidence-archive-manifest-v1.schema.json` validates a private evidence archive manifest.
+- `isac-handoff-v1.schema.json` validates a bounded draft handoff for authenticated ISAC intake.
+- `examples/classification/` contains one valid and one invalid classification for each family, including explicit `unknown` abstention.
+- `examples/archive/` and `examples/handoff/` exercise each versioned document schema.
+
+The schemas use JSON Schema Draft 2020-12, internal `$ref` values, standard formats, and no implementation-specific keywords. Python `jsonschema` and TypeScript validators such as Ajv can compile the files without model conversion. Consumers must reject a document unless `schema_version` equals the schema's `const` value. Consumers must also run semantic reference validation because JSON Schema cannot prove that an ID points to an item in another array.
+
+## Evidence Rules
+
+Capture workers store source text, a normalized value, confidence, engine identity, an image digest, a bounded region, and append-only correction history for each evidence value. A null normalized value requires a `missing_reason`. A present normalized value requires a null `missing_reason`. Each correction's `before` state must match the preceding `after` state. Timestamps must increase, and the final `after` state must match the current evidence value.
+
+Workers record the configured item shown on screen under `observed_instances`, including its visible level, quality, tier, upgrade state, and values. Workers place proposed reusable definitions under `canonical_candidates` and handoff `records`. A worker must not copy an observed roll, relationship, mechanic, range endpoint, or option list into a canonical candidate unless evidence establishes that canonical claim.
+
+## Trust Boundary
+
+Archive and handoff documents contain content hashes and logical artifact IDs. They exclude host paths and credentials. The handoff declares `mutation_authority: "none"`. Importing or inspecting it grants no permission and performs no mutation. An authenticated ISAC action must revalidate each draft and preserve contributor moderation and audit behavior.
+
+Archive images and handoff images allow at most 64 MiB. Private archive videos allow at most 16 GiB, matching the configured capture ceiling. Schema validation enforces media-specific byte limits. Semantic validation enforces unique entity and correction IDs, local references, evidence artifact hashes, correction chains, and normalized image bounds.
+
+The contracts assign explicit states or reasons to cancellation, resource exhaustion, ambiguous classification, unsupported content, and extraction failure. Recovery requires a listed transition. Unknown transitions and future schema versions fail closed.