feat(federation): certify graph profile and evaluation

[tcballard]

Purpose

This restores the clean graph-certification review edge after #465 was merged into an intermediate branch.

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

What this slice adds

• v2-first decided init --parent-corpus guidance with preserved no-guidance output
• graph-complete DecisionGrounding fixtures and committed quality floors
• CLI documentation, roadmap evidence, and end-to-end certification material
• exact compatibility with v1 and no-manifest repositories

Stack

• Base: graph-engine activation
• Head: agent/federation-12-graph-certification
• Next: feat(federation): ship v0.29.0 federation #469, the final v0.29.0 observability and forge-neutral release slice

This supersedes #465 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Superseded by #469, which now integrates the exact final intended v0.29.0 tree on current main.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.