fix(heavy): sync_lock_regression — pass --no-embed so CI runs measure lock contention, not key absence

Heavy tests workflow run 26542545802 (commit 7962d312, after the
previous fm_wallclock fix) failed at the next heavy script in the chain:

  [sync_lock_regression] outcomes: winners=0 losers=0 unknown=4
  [sync_lock_regression] FAIL: expected 1 winner, got 0
  [sync_lock_regression] FAIL: expected 3 lock-busy losers, got 0

Each of the 4 parallel `gbrain sync` invocations failed for the same
reason — none of them ever even got to the lock-acquire step:

    Embedding model "zeroentropyai:zembed-1" requires ZEROENTROPY_API_KEY.
    Re-run with --no-embed to import-only and embed later once the key is set.

The CI runner doesn't pipe any embedding-provider API keys (deliberate —
heavy tests measure ops shape, not LLM behavior), and sync now hard-fails
when its embed step can't reach a configured provider.

This script measures the writer-lock race shape — `gbrain-sync` row in
`gbrain_cycle_locks`, exactly-one-winner semantics, N-1 fail-fast losers
with "Another sync is in progress", zero leaked rows post-run. It never
needed embeddings; the original write predates the hard-require landing.

Fix: pass `--no-embed` to the sync invocation. Same kind of fix as
fm_wallclock (commit 7962d312) but on the sync side rather than init.

No production code touched. One-line change in the bash script.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/heavy/sync_lock_regression.sh

@@ -91,7 +91,11 @@ for ((i=1; i<=NUM_PARALLEL; i+=1)); do
   OUT_F=$(mktemp -t sync-lock-out-XXXXXX)
   EXIT_FILES+=("$EXIT_F")
   OUT_FILES+=("$OUT_F")
-  ( bun run src/cli.ts sync --dir "$BRAIN_DIR" >"$OUT_F" 2>&1; echo $? > "$EXIT_F" ) &
+  # --no-embed: this test measures the writer-lock race, not embeddings.
+  # CI runners don't pipe ZEROENTROPY_API_KEY / OPENAI_API_KEY / VOYAGE_API_KEY,
+  # so without --no-embed every sync fails with "Embedding model X requires Y"
+  # and the test classifier reports unknown failures instead of lock outcomes.
+  ( bun run src/cli.ts sync --dir "$BRAIN_DIR" --no-embed >"$OUT_F" 2>&1; echo $? > "$EXIT_F" ) &
   PIDS+=($!)
 done