fix: adversarial review fixes — failure shape, CHANGELOG guard, vet coherence

Claude adversarial subagent findings (11), all verified before applying:
- The dispatch JSON contract gains an explicit FAILURE shape
  ({"error":...}) and a parent branch for it — a doc-sync that could not
  run (spawned marking failed, broken preamble) previously had only the
  no-updates shape to emit, which the parent printed as 'Documentation is
  current': a silent false-clean of exactly the VAS-449 class.
- Scope guard now covers CHANGELOG: skip Step 5 voice polish and resolve
  CHANGELOG-touching gates to leave-as-is (the parent authored the
  release entry; the prompt's older auto-choose clause conflicted with
  the contract's never-rewrite invariant).
- Recovery vet is sequence-coherent: pushing a commit pushes its
  ancestors, so ANY non-doc commit (VERSION, package.json, CHANGELOG.md)
  blocks the whole sequence — no more push-the-vetted-child-of-an-
  unvetted-parent hole.
- Steps 7/8/10 failure branches stop a still-running backgrounded task
  before falling back, so a late result never races the inline audit.
- 'Documentation synced' print gated on pushed:true (item 6 owns the
  local-only outcome); doc-review skip note's backward step pointer
  fixed; foreground note scoped 'at initial dispatch' so the sanctioned
  inline FALLBACKS in Steps 7/8 read as sanctioned; constants docstring
  no longer overclaims single-sourcing (names the 3 inline templates).
- Runtime-hook TODO raised P2 → P1: the spawned trust chain is
  agent-self-asserted; prose cannot close it, the hook can.

Both docsync gate E2Es re-verified green on the amended prompt, including
the strict run_in_background === false dispatch assert.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

document-release/sections/release-body.md

@@ -433,8 +433,8 @@ not an opt-in. The user turns it off only by asking explicitly
 
 **Spawned-session skip** (per the spawned-dispatch contract at the top of this skill): in a
 spawned session, skip this entire section — the dispatching workflow owns its own review
-passes, and the apply gate below needs a human. Note the skip in your completion report and
-continue with Step 9's doc health summary.
+passes, and the apply gate below needs a human. Note the skip in your completion report (the
+Step 9 doc health summary you already produced) and finish the workflow.
 
 **Preflight — decide whether and how the doc review runs:**