feat(consistency): distributed multi-machine safety (CUST-WP-0026)

T01 — No-regress rule (C-15): fix-consistency now detects when a DB task
status is ahead of the workplan file (e.g. marked done on CoulombCore)
and emits C-15 WARN instead of regressing the DB back to the stale file
value. STATUS_ORDER ranking: todo(0) < in_progress/blocked(1) < done/cancelled(2).

T02 — Pull gate (C-16): fix_repo runs git fetch + rev-parse at the start
of every --fix run. If the local repo is behind its remote tracking branch,
all write operations are skipped and C-16 WARN is emitted. Best-effort:
offline/no-remote silently skips the check.

T03 — DB→file writeback: C-15 fix path patches the status field in the
matching task block and git-commits the change with a standard message.
--no-writeback flag disables writeback while keeping T01/T02 active.

T04 — CLAUDE.md + session-protocol.template updated with new guidance,
C-15/C-16 semantics, and fix-consistency-remote recommendation.

T05 — Makefile: fix-consistency-remote pulls then fixes in one step.

16 new tests; 155 passed total.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/project_rules/session-protocol.template

@@ -42,7 +42,16 @@ If no workstreams: follow First Session Protocol (`first-session.md`).
 ```
 add_progress_event(summary="...", topic_id="{TOPIC_ID}", workstream_id="<uuid>")
 ```
-If workplan files were modified:
+If workplan files were modified, ensure the local copy is up to date first:
 ```bash
+git -C <repo_path> pull --ff-only
 cd ~/the-custodian/state-hub && make fix-consistency REPO={REPO_SLUG}
 ```
+For repos where implementation runs on a remote machine (e.g. CoulombCore),
+use the combined target which pulls before fixing:
+```bash
+cd ~/the-custodian/state-hub && make fix-consistency-remote REPO={REPO_SLUG}
+```
+**C-15** (DB task ahead of file) is normal in multi-machine workflows — writeback
+will sync the file to match DB.  **C-16** (repo behind remote) blocks all writes
+until you pull — intentional to prevent clobbering remote progress.