chore: fixture backlog for Phase A toy run + gitignore cleanup

- fixtures/phase-a-toy.json — scaffold source for `autoresearch start`
  Phase A live run: val_vol_r2 metric, daily EUR/USD, HEPA encoder toy
- .gitignore: add runs/ (ephemeral run dirs), metrics.json, embeddings.json,
  HEARTBEAT, STATUS.md, pyc/__pycache__/.pytest_cache, eval binary
- untrack metrics.json (was a stale committed sample, now gitignored)

Launch on koala:
  python scripts/autoresearch_start.py fixtures/phase-a-toy.json phase-a-toy
  op run -- env LITELLM_KEY="$LITELLM_KEY" \
    python loop.py --run-dir runs/phase-a-toy --iters 3

Closes the last gate on jepa-fx-risk#11 Phase A (code shipped v1.4.0;
live run pending).

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

.gitignore

@@ -34,3 +34,20 @@ bin/
 
 # downloaded + processed market data (track via DVC/MinIO, #10 — not git)
 data/
+
+# autoresearch run dirs (ephemeral; each scaffold rebuilds from fixtures/)
+runs/
+
+# ephemeral experiment outputs (generated by train.py / loop.py)
+metrics.json
+embeddings.json
+HEARTBEAT
+STATUS.md
+
+# python caches
+__pycache__/
+*.pyc
+.pytest_cache/
+
+# built Go binaries
+eval