Memory Integrity: Carryover Overview Coverage & Body-Staleness Gates

Agents Remember 2.6.0

Closes #56: everything closeout writes into task memory now has a carryover
path home, and verification metadata can no longer advance over stale
onboarding bodies.

Highlights

• Branch-memory carryover now plans route-overview candidates beside file
  sidecars and regenerates official-side route indexes after a carry.
• Closeout gains body/history gates: header-only or unmarked history-only
  onboarding refreshes fail for changed sources and their nearest-governing
  route overviews.
• New in-band attestation convention: explicit No content impact: /
  No route impact: Update History markers record reviewed-no-impact
  decisions and are surfaced in closeout tool responses.

Onboarding And Memory

• Carryover candidates are kind-tagged (file-sidecar / route-overview);
  overview candidates are keyed by the normalized code route (. for the repo
  root) and selected via the existing include_review_required.
• Identical branch/official overview content auto-carries for metadata
  re-verification only — closing the post-merge gap where overview
  verification stayed pinned at the pre-merge commit. Differing content is
  always review-required: overview bodies are model-authored aggregates.
• overview.index.json files are derived artifacts: regenerated on the
  official side after a carry (never copied), guarded on a clean checkout of
  the official ref, and reported as route_index_refresh.

Closeout Gates

• The sidecar content gate became a four-case body/history classification:
  body+history passes; a body edit without an Update History entry fails
  (traceability); a history-only edit passes only with the
  No content impact: marker; metadata-only refreshes fail.
• Route overviews get the same gate scoped by domain evidence: only the
  nearest-governing overview of a changed path gates closeout; overviews
  matched as ancestors are reported as stamped_without_body_review instead.
• Closeout previews expose the full gate classifications
  (sidecar_body_gate, route_overview_body_gate); apply payloads surface
  every attested document so marker use stays reviewable at the commit gate.
• The c-05 onboarding skill documents the body-before-metadata doctrine and
  both marker conventions (packaged + all harness starter mirrors).

Internals

• New kernel/onboarding_doc.py owns shared onboarding-document parsing,
  route-overview discovery, and the meaningful-body/history classification;
  worktrees/modules/onboarding.py re-exports the moved helpers (facade).