fix: make documentation release review and publication consistent

Review before commit, clarify changelog safeguards and unavailable reviewer modes, and preserve raw PR bodies across separate shell calls. Keep title sync in one shell and add regression coverage.

Co-authored-by: OpenAI Codex <noreply@openai.com>

document-release/SKILL.md

@@ -445,8 +445,7 @@ You are running the `/document-release` workflow. This runs **after `/ship`** (c
 exists or about to exist) but **before the PR merges**. Your job: ensure every documentation file
 in the project is accurate, up to date, and written in a friendly, user-forward voice.
 
-You are mostly automated. Make obvious factual updates directly. Stop and ask only for risky or
-subjective decisions.
+Make factual updates directly; ask about risky or subjective decisions.
 
 **When dispatched as a subagent (spawned session):** spawned mode triggers ONLY from the
 preamble's `SESSION_KIND: spawned` STATUS echo — a dispatching workflow marks the session by
@@ -502,20 +501,29 @@ sections. Read a section in full before doing its step; do not work from memory.
 
 ## Step 1: Pre-flight & Diff Analysis
 
+`<base>` and the hosting platform come from the shared Step 0 above this workflow.
+Resolve the release merge-base, stopping if neither ref exists.
+Use the printed SHA for `<diff-base>` in later commands, not a shell variable:
+
+```bash
+DOC_DIFF_BASE=$(git merge-base origin/<base> HEAD 2>/dev/null || git merge-base <base> HEAD) || exit 1
+echo "DOC_DIFF_BASE: $DOC_DIFF_BASE"
+```
+
 1. Check the current branch. If on the base branch, **abort**: "You're on the base branch. Run from a feature branch."
 
 2. Gather context about what changed:
 
 ```bash
-git diff <base>...HEAD --stat
+git diff <diff-base> HEAD --stat
 ```
 
 ```bash
-git log <base>..HEAD --oneline
+git log <diff-base>..HEAD --oneline
 ```
 
 ```bash
-git diff <base>...HEAD --name-only
+git diff <diff-base> HEAD --name-only
 ```
 
 3. Discover all documentation files in the repo:
@@ -540,7 +548,7 @@ Before touching any documentation file, build a **coverage map** of what shipped
 documented. This is inspired by the Diataxis framework (tutorial / how-to / reference / explanation)
 — but applied as an audit lens, not a generation tool.
 
-1. **Extract public surface changes from the diff.** Scan `git diff <base>...HEAD` for:
+1. **Extract public surface changes from the diff.** Scan `git diff <diff-base> HEAD` for:
    - New exported functions, classes, commands, CLI flags, config options, API endpoints
    - New skills, workflows, or user-facing capabilities
    - Renamed or removed public surface (modules, commands, features)