Initial scaffold: image/ FastAPI app, models.yaml, docs

- image/ FastAPI app: /api/status, /api/swap, /api/swap/{id}/stream, /api/test-connection
- models.yaml: 5-model catalog (qwen3-vl, gemma4, qwen36, qwen3-235b-fp8, qwen25-72b)
- README, runbook, known-issues
- Dry-run swap verified against live Spark 1 (gemma4 currently loaded)

.gitignore

@@ -0,0 +1,14 @@
+__pycache__/
+*.py[cod]
+*.egg-info/
+.venv/
+venv/
+.env
+.env.*
+!.env.example
+node_modules/
+*.s9pk
+dist/
+build/
+.DS_Store
+.claude/