Decision sheet D1-D10: hub CHANGELOG, architecture notes (01, 04, 05, 07, 08, 10), register (VERIFY states, R-912), STATUS, report; decoy suite runs in a git worktree

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

scripts/CHANGELOG.md

@@ -1,3 +1,10 @@
+## gates — the decoy suite runs in a linked git worktree (2026-10-08, fixed without a row)
+
+- `test_gate_decoys.py` took its lock at `ROOT/.git/decoy-suite.lock`; in a `git worktree add` copy `.git` is a FILE, so
+  the suite crashed (`NotADirectoryError`) and `repo_gates.py` went red for every helper working in a worktree. The lock
+  now lives in `git rev-parse --absolute-git-dir` (per worktree — each worktree mutates its own files), falling back to
+  `ROOT/.git`. Measured: the full `repo_gates.py --fast` run green inside `worktrees/hub-integ`.
+
 ## gates — site gate 20: the one picture viewer (2026-10-08)
 
 - Every `data-gallery` opener must be an `<a href>` to an existing file under `website/assets/`; a page with openers must

scripts/test_gate_decoys.py

@@ -39,7 +39,15 @@ ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
 # already mutated, and B's "restore" then wrote A's decoy back for good: website/en/apps.html was left without its
 # Radicale logo, one step from a push. An exclusive lock makes a second run WAIT for the first.
 import fcntl
-_LOCK = open(os.path.join(ROOT, ".git", "decoy-suite.lock"), "w")
+# The lock lives in THIS worktree's git dir: in a linked worktree (`git worktree add`) `.git` is a FILE, and the old
+# `ROOT/.git/decoy-suite.lock` crashed with NotADirectoryError (2026-10-08). Each worktree mutates its own files, so a
+# per-worktree lock is the right scope.
+try:
+    _GITDIR = subprocess.run(["git", "rev-parse", "--absolute-git-dir"], cwd=ROOT, capture_output=True, text=True,
+                             check=True).stdout.strip()
+except (OSError, subprocess.CalledProcessError):
+    _GITDIR = os.path.join(ROOT, ".git")
+_LOCK = open(os.path.join(_GITDIR, "decoy-suite.lock"), "w")
 fcntl.flock(_LOCK, fcntl.LOCK_EX)
 
 # ── WHAT THIS FILE COVERS ────────────────────────────────────────────────────────────────────────