harness: gitignore tmp/ + add promotion check to /save and /scc

- .gitignore: ignore root tmp/ (temp/ and .claude/tmp/ were already ignored;
  root tmp/ was not, which is how scratch got committed and needed cleanup).
- New .claude/scripts/tmp-promotion-check.sh: advisory, read-only, never blocks.
  Scans the gitignored scratch dirs (tmp/, temp/, .claude/tmp/) and flags files
  worth graduating (scripts, substantial docs, session-log-referenced) before
  they're lost to cleanup. Silent when scratch is empty.
- /save (Phase 4) and /scc (new step 2) run the check before sync.sh, pointing
  at .claude/TEMP_GRADUATION.md for the graduate-vs-delete decision.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/commands/save.md

@@ -102,6 +102,18 @@ not on every save.
 
 ## Phase 4 — Sync
 
+First, run the **promotion check** — the scratch dirs (`tmp/`, `temp/`, `.claude/tmp/`)
+are gitignored, so anything in them is invisible to git and lost on cleanup. This is
+advisory and never blocks:
+
+```bash
+bash .claude/scripts/tmp-promotion-check.sh
+```
+
+If it flags `[GRADUATE?]` candidates, graduate the keepers per `.claude/TEMP_GRADUATION.md`
+(`git mv` into `scripts/` / `clients/<x>/reports/` / `projects/<p>/tools/`) **before** the
+sync sweeps the commit. Pure scratch can be left or deleted. Then sync:
+
 ```bash
 bash .claude/scripts/sync.sh
 ```