docs: accept repository classification boundary

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a0230c-b06c-7641-808a-e191b6d1da49

docs/adr/ADR-0002-repository-classification-projections.md

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+# ADR-0002: Consume repository classification as a projection
+
+**Status:** Accepted
+**Date:** 2026-08-22
+**Workplan:** `HUB-WP-0006-T01`
+**Upstream contract:** `RMGR-CONTRACT-CLASSIFICATION-0001` version 1.0
+
+## Context
+
+State Hub's legacy topic spine mixes mutable topic rows with repository
+classification and navigation. State Hub retirement slice A5 replaces that
+model. Repo Manager now validates each repository-authoritative
+`.repo-classification.yaml` and publishes the validated classification in its
+repository projection.
+
+Hub-core owns cross-domain projection and navigation, but it must not turn the
+projection into a second classification authority or recreate a mutable topic
+table.
+
+## Decision
+
+1. Repo Manager's classification contract version 1.0 is accepted without a
+   schema gap. Repo Manager owns validation and publication; the repository
+   file remains authoritative.
+2. Hub-core consumes only validated Repo Manager projections through a
+   versioned `port.repo` boundary. It does not read, validate, infer, coerce, or
+   write `.repo-classification.yaml` directly.
+3. Hub-core may aggregate repositories by primary domain, secondary domain,
+   category, capability tag, business stake, and business mechanic for
+   navigation and hub composition. Every derived view carries Repo Manager
+   source identity, repository revision, contract version, and rebuild time.
+4. A legacy State Hub topic identifier may be retained as a compatibility
+   alias during A5 cutover. It is not a new authority and must have an expiry
+   or residual owner.
+5. Invalid or unsupported projection versions fail closed and remain visible
+   as diagnostics. Hub-core does not silently reinterpret them.
+6. State Hub owns the A5 consumer-route switch and rollback flag under
+   `STATE-WP-0079`. Hub-core owns the receiving projection/query and navigation
+   surface; Repo Manager owns the input contract.
+
+## Consequences
+
+- Topic navigation becomes rebuildable from repository authority rather than
+  copied from the State Hub `topics` table.
+- Repository classification changes continue through governed Repo Manager
+  mutation and repository review, never a hub-core write endpoint.
+- Hub-core needs an explicit Repo Manager client, projection schema, query/MCP
+  surface, provenance checks, and unavailable/version-mismatch behavior before
+  A5 can switch.
+- Contract evolution is negotiated by version; a canon vocabulary change is
+  not inferred from observed data.