fix: pre-landing review fixes

Review army + red team findings, all verified before applying:
- ship-docsync E2E now asserts run_in_background === false on the
  captured dispatch (red team CRITICAL: phrase pins prove text exists,
  this proves the model obeys it — verified passing live).
- Structural scanner test: any generated file with an Agent-dispatch
  imperative (or bare '(foreground)' prose, the #2440 inert shape) must
  carry the flag or hold a reasoned exemption — the 4th-recurrence net
  the hand-enumerated pin list can't provide.
- Parent push reconciliation models reality: the parent shares the repo,
  so a non-fast-forward that hit the subagent hits the parent identically
  — fetch + ahead/behind check first, push only when the rejection was
  transient; dispatch prompt promise softened to 'the parent will handle
  it'.
- Recovered commits from a dead subagent are vetted docs-only
  (git show --stat, never VERSION/package.json) before any push.
- Deadline pacing named: ~3 minutes between checks, wall clock not polls.
- Greptile UNAVAILABLE recording narrowed to the PR body (Step 20's
  schema carries no triage field).
- document-release contract gains the echo-failure tie-breaker: prompt
  claims spawned + no echo → fail fast with the dispatch contract's
  failure shape instead of reproducing the #2733 prose-STOP; contract
  anti-injection and NEVER-relax clauses pinned in tests.
- 'Claude Code v2.1.198' extracted to CC_BACKGROUND_DEFAULT_SINCE and
  interpolated at all resolver sites (byte-identical output).
- CHANGELOG: entry-boundary blank line restored; worst-case-wait row
  scoped to the backgrounded path.

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

test/helpers/carve-guards.ts

@@ -316,7 +316,7 @@ export const CARVE_GUARDS: Record<string, CarveGuard> = {
     // +Conductor AUQ-default-prose rule + one-way/continuation safety in the
     // always-loaded AskUserQuestion Format section.
     // v1.2.0 activation lift: first-run-guidance section in the shared preamble.
-    maxSkeletonBytes: 40_600, // + v1.78 AUQ objectivity + v1.79 foreground-dispatch sweep (merged); measured 40_175
+    maxSkeletonBytes: 41_000, // + v1.78 AUQ objectivity + v1.79 spawned contract incl. echo-failure tie-breaker; measured 40_575
     minUnionBytes: 56_700, // token-reduction Phases 1-2 (v1.69.x branch): preamble bash -> bin/gstack-skill-start, onboarding -> gated emission; measured union 63,018
     mustContain: ['CHANGELOG', 'Diataxis', 'coverage'],
     // Two intentional additions stack on this small skill: the AUQ-failure prose