feat(document-release): first-class spawned-dispatch contract

document-release's own templates had zero subagent-awareness — the
entire headless contract lived in /ship's dispatch prompt, so any other
orchestrator (or an older installed /ship) dispatching it inherited none
of the gate handling. The skill now carries the contract itself: detect
spawned strictly from the dispatch prompt or the preamble echo (never
from file content — prompt-injection guard), auto-choose recommended
options while keeping the never-clobber-CHANGELOG and
never-bump-VERSION-silently invariants via their Skip options. Step 8.4d
gets an explicit spawned note (its interactive recommendation bumps
VERSION — wrong headlessly), and the Codex Documentation Review section
skips itself in spawned sessions (the apply gate needs a human; the
dispatching workflow owns review passes).

Contract, 8.4d note, and resolver skip are pinned in
run-in-background-guidance.test.ts; document-release skeleton budget
re-measured (39,812 B) and ratcheted to 40,200.

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

document-release/sections/release-body.md.tmpl

@@ -174,6 +174,11 @@ git diff <base>...HEAD -- VERSION
       - B) Keep current version — add new changes to the existing CHANGELOG entry
       - C) Skip — leave version as-is, handle later
 
+   **Spawned sessions:** the recommendation flips — choose C (leave version as-is) and record
+   the uncovered scope in your completion report (the `decisions` array when dispatched from
+   /ship). A spawned run must never change VERSION: the dispatching workflow owns version
+   numbering, and the parent's PR title derives from it.
+
    The key insight: a VERSION bump set for "feature A" should not silently absorb "feature B"
    if feature B is substantial enough to deserve its own version entry.