docs: update README, runbook, and steering files for today's changes

- README: added AI agent management section, updated paper trading
  description (no manual capital controls, broker-synced reset)
- Steering: migration numbers updated to 027 (next: 028), added
  trading engine endpoint, ruff pinning and isort config notes
- Runbook: already had reset/Alpaca sections from earlier commits

.kiro/steering/development-process.md

@@ -22,7 +22,9 @@
 - Frontend: Vitest + MSW (Mock Service Worker) for deterministic API mocking, tests in `frontend/src/test/`
 - Run Python tests: `python -m pytest tests/ -x --tb=short -q`
 - Run frontend tests: `cd frontend && npx vitest --run`
-- Lint Python: `nix-shell -p ruff --run "ruff check services/"`
+- Lint Python: `nix-shell -p ruff --run "ruff check services/"` (or `.venv/bin/ruff check services/`)
+- Ruff is pinned to `ruff==0.15.10` in `requirements.txt` — CI uses the same version
+- Ruff config: `ruff.toml` with `known-first-party = ["services"]` for consistent import sorting
 - Pre-existing test failures (not regressions): `test_extractor_prompts.py`, `test_extractor_schemas.py`, `test_filings_adapter.py`, `test_ollama_client.py`
 
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