fix(workflows): assert HEAD on per-agent branch before worktree commits (#2924) (#2941)

* fix(workflows): assert HEAD on per-agent branch before worktree commits

Worktree-mode setup could leave HEAD attached to a protected branch (master),
causing agent commits to land there. The previous response was a destructive
self-recovery via 'git update-ref refs/heads/master <sha>', which silently
rewinds the protected branch and destroys concurrent commits in multi-active
scenarios (parallel agents, user committing while agent runs).

- Reorder <worktree_branch_check> in execute-phase.md and quick.md to assert
  HEAD via 'git symbolic-ref' BEFORE any 'git reset --hard'. HALT with a
  blocker if HEAD is on main/master/develop/trunk/release/* or detached.
- Add a per-commit HEAD assertion (step 0) to gsd-executor.md
  <task_commit_protocol>; HEAD attachment can drift after 'git checkout <sha>'.
- Forbid 'git update-ref refs/heads/<protected>' in
  <destructive_git_prohibition>; surface the blocker rather than self-heal.
- Remove '--no-verify' as the worktree-mode default in execute-phase.md,
  execute-plan.md, quick.md, and references/git-integration.md. Hooks now
  run on every executor commit; opt out only via workflow.worktree_skip_hooks.
- Add regression test that parses the worktree_branch_check blocks structurally
  and asserts the symbolic-ref check precedes the reset --hard, no workflow
  performs update-ref on a protected ref, and --no-verify is no longer the
  default in any parallel-execution prompt.

* fix(#2924): address CodeRabbit review findings on worktree HEAD PR

- Add positive worktree-agent-* allow-list to <task_commit_protocol> step 0
  in gsd-executor.md and to <worktree_branch_check> in execute-phase.md and
  quick.md. The deny-list (main|master|develop|trunk|release/*) silently
  allowed feature/* and other arbitrary branches outside the agent namespace.
- Register workflow.worktree_skip_hooks in both config schemas
  (sdk/src/query/config-schema.ts and get-shit-done/bin/lib/config-schema.cjs)
  and document it in docs/CONFIGURATION.md so config-set accepts it.
- Fix stash lifecycle in execute-phase.md post-wave hook validation: stash
  under a named ref and pop after the hook run; warn on pop failure.
- Pre-dispatch PLAN.md commit in quick.md: gate on git diff --cached --quiet
  for idempotency and exit 1 with a clear error on commit failure (both the
  --no-verify and the normal branches) — no more swallowing real errors.
- Test fixes (tests/bug-2924-worktree-head-attachment.test.cjs):
  - Parse the protected-branch alternation structurally and require
    main, master, develop, trunk, release/.* (release/* was previously
    skipped by the \\b...\\b regex).
  - Use fs.readdirSync(dir, { recursive: true }) so workflows in nested
    subdirectories are also asserted against the update-ref ban.
  - Add allow-list assertions for execute-phase.md, quick.md, and
    gsd-executor.md to lock in the new positive namespace check.

* test(#2924): assert sub-section end marker exists before slicing

* test(#2924): use section boundary instead of fixed window for parallel-agents slice

agents/gsd-executor.md

@@ -358,6 +358,30 @@ If RED or GREEN gate commits are missing, add a warning to SUMMARY.md under a `#
 <task_commit_protocol>
 After each task completes (verification passed, done criteria met), commit immediately.
 
+**0. Pre-commit HEAD safety assertion (worktree mode only, MANDATORY before every commit — #2924):**
+When running inside a Claude Code worktree (`.git` is a file, not a directory), assert HEAD is on a per-agent branch BEFORE staging or committing. If HEAD has drifted onto a protected ref, HALT — never self-recover via `git update-ref refs/heads/<protected>`:
+```bash
+if [ -f .git ]; then  # worktree
+  HEAD_REF=$(git symbolic-ref --quiet HEAD || echo "DETACHED")
+  ACTUAL_BRANCH=$(git rev-parse --abbrev-ref HEAD)
+  # Deny-list: never commit on a protected ref.
+  if [ "$HEAD_REF" = "DETACHED" ] || \
+     echo "$ACTUAL_BRANCH" | grep -Eq '^(main|master|develop|trunk|release/.*)$'; then
+    echo "FATAL: refusing to commit — worktree HEAD is on '$ACTUAL_BRANCH' (expected per-agent branch)." >&2
+    echo "DO NOT use 'git update-ref' to rewind the protected branch — surface as blocker (#2924)." >&2
+    exit 1
+  fi
+  # Positive allow-list: HEAD must be on the canonical Claude Code worktree-agent
+  # branch namespace (`worktree-agent-<id>`). This catches feature/* and any other
+  # arbitrary branch that the deny-list would silently allow (#2924).
+  if ! echo "$ACTUAL_BRANCH" | grep -Eq '^worktree-agent-[A-Za-z0-9._/-]+$'; then
+    echo "FATAL: refusing to commit — worktree HEAD '$ACTUAL_BRANCH' is not in the worktree-agent-* namespace." >&2
+    echo "Agent commits must live on per-agent branches; surface as blocker (#2924)." >&2
+    exit 1
+  fi
+fi
+```
+
 **1. Check modified files:** `git status --short`
 
 **2. Stage task-related files individually** (NEVER `git add .` or `git add -A`):
@@ -426,6 +450,15 @@ back, those deletions appear on the main branch, destroying prior-wave work (#20
 - `git rm` on files not explicitly created by the current task
 - `git checkout -- .` or `git restore .` (blanket working-tree resets that discard files)
 - `git reset --hard` except inside the `<worktree_branch_check>` step at agent startup
+- `git update-ref refs/heads/<protected>` (where protected is `main`, `master`,
+  `develop`, `trunk`, or `release/*`). This is an absolute prohibition (#2924).
+  If you discover that your worktree HEAD is attached to a protected branch and your
+  commits landed there, **DO NOT** "recover" by force-rewinding the protected ref —
+  that silently destroys concurrent commits in multi-active scenarios (parallel
+  agents, user committing while you run). HALT and surface a blocker. The setup-time
+  `<worktree_branch_check>` and per-commit `<pre_commit_head_assertion>` are the
+  correct prevention; if either fails, the workflow MUST stop, not self-heal.
+- `git push --force` / `git push -f` to any branch you did not create.
 
 If you need to discard changes to a specific file you modified during this task, use:
 ```bash