feat(federation): activate verified corpus graphs

[tcballard]

Purpose

This restores the clean graph-engine activation review edge after #464 was merged into an intermediate branch.

The source tree is unchanged from the previously validated activation. The commit was rewritten only to add the explicitly authorized DCO trailer and restore linear ancestry.

What this slice activates

• one verified DAG-aware retained/effective/local corpus model
• shared resolution across CLI, enforcement, retrieval, routing, gate, Sentry, exports, MCP, and audit
• global source qualification with deterministic equal-ID ambiguity
• Decision-backed override chains and diamond convergence
• closure generation v3, store/v3, freshness, and fail-closed corruption handling
• complete source, layer, pin, topology-route, and override provenance
• read-only enforcement for all inherited materialisation routes
• exact v1 and no-manifest compatibility

Stack

• Base: graph foundation
• Head: agent/federation-11-graph-engine
• Next: graph profile and evaluation certification

This supersedes #464 as the mergeable review edge. Hosted CI is rerunning on the exact signed head.

[tcballard]

Superseded by #469, which now integrates the exact final intended v0.29.0 tree on current main. This PR is being closed only to remove the obsolete squash-stack edge; its branch and review history remain available.