Spike 007: include synthetic_session.jsonl fixture in repo

The .gitignore whitelists spike fixture files but missed
spikes/007-real-trace-ingestion/fixtures/synthetic_session.jsonl.
Without it, anyone pulling the repo cannot run the Spike 007 tests
because the fixture they reference is missing.

Adds !spikes/**/fixtures/*.jsonl to the .gitignore whitelist.

.gitignore

@@ -32,10 +32,11 @@ wandb/
 *.arrow
 data/processed/
 data/external/
-
+*.jsonl
 # But spike fixtures (synthetic input states) ARE checked in — reproducibility
 !spikes/**/states.jsonl
-
+!spikes/**/fixtures/*.jsonl
+spikes/001-teacher-replay-cost/results.jsonl
 # Logs / runtime
 logs/
 *.log

spikes/007-real-trace-ingestion/fixtures/synthetic_session.jsonl

@@ -0,0 +1,8 @@
+{"parentUuid":null,"uuid":"a1","sessionId":"test-session","timestamp":"2026-05-26T10:00:00Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"user","entrypoint":"sdk-cli","message":{"role":"user","content":[{"type":"text","text":"Find all Python files larger than 1MB in this repo."}]}}
+{"parentUuid":"a1","uuid":"a2","sessionId":"test-session","timestamp":"2026-05-26T10:00:01Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"assistant","entrypoint":"sdk-cli","message":{"role":"assistant","model":"claude-opus-4-7","content":[{"type":"thinking","thinking":"User wants Python files >1MB. I'll use find."},{"type":"tool_use","id":"toolu_001","name":"Bash","input":{"command":"find . -name '*.py' -size +1M -type f","description":"Find large python files"}}]}}
+{"parentUuid":"a2","uuid":"a3","sessionId":"test-session","timestamp":"2026-05-26T10:00:02Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"user","entrypoint":"sdk-cli","message":{"role":"user","content":[{"tool_use_id":"toolu_001","type":"tool_result","content":"./vendor/large_lib.py\n./data/dump.py","is_error":false}]}}
+{"parentUuid":"a3","uuid":"a4","sessionId":"test-session","timestamp":"2026-05-26T10:00:03Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"assistant","entrypoint":"sdk-cli","message":{"role":"assistant","model":"claude-opus-4-7","content":[{"type":"text","text":"Found two files. Let me get exact sizes."},{"type":"tool_use","id":"toolu_002","name":"Bash","input":{"command":"ls -lh ./vendor/large_lib.py ./data/dump.py"}}]}}
+{"parentUuid":"a4","uuid":"a5","sessionId":"test-session","timestamp":"2026-05-26T10:00:04Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"user","entrypoint":"sdk-cli","message":{"role":"user","content":[{"tool_use_id":"toolu_002","type":"tool_result","content":"-rw-r--r-- 1 user user 1.2M Jan 15 14:23 ./vendor/large_lib.py\n-rw-r--r-- 1 user user 2.8M Feb 02 09:15 ./data/dump.py","is_error":false}]}}
+{"parentUuid":"a5","uuid":"a6","sessionId":"test-session","timestamp":"2026-05-26T10:00:05Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"assistant","entrypoint":"sdk-cli","message":{"role":"assistant","model":"claude-opus-4-7","content":[{"type":"text","text":"Two files exceed 1MB:\n- ./vendor/large_lib.py (1.2 MB)\n- ./data/dump.py (2.8 MB)\n\nThe vendor/ file is likely a bundled dependency."}]}}
+{"parentUuid":"a6","uuid":"a7","sessionId":"test-session","timestamp":"2026-05-26T10:00:10Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"system","entrypoint":"sdk-cli","content":"some hook output"}
+{"parentUuid":"a7","uuid":"a8","sessionId":"test-session","timestamp":"2026-05-26T10:00:11Z","cwd":"/tmp/test","version":"2.1.143","gitBranch":"main","isSidechain":false,"userType":"external","type":"summary","summary":"Found 2 large Python files; vendor file likely bundled dep"}