COMMIT_MESSAGE.txt

feat: implement get_orderbook tool for Stellar DEX market analysis

Add comprehensive orderbook retrieval and analysis tool with 11 derived
analytics fields including spread, mid price, liquidity depth, and
orderbook imbalance.

Analytics implemented:
- Best bid/ask, mid price, spread, spread percentage
- Total bid/ask liquidity
- Bid/ask depth at configurable price levels (1%, 2%, 5%)
- Orderbook imbalance (-1 to +1 scale)
- Weighted average bid/ask prices

Key features:
- Decimal arithmetic using BigInt (no floating point errors)
- Graceful empty orderbook handling
- Comprehensive error handling (INVALID_ASSET, MISSING_ISSUER, RATE_LIMITED, HORIZON_UNAVAILABLE)
- Auto-clamping limit to [1, 200]
- 100% test coverage with 15+ unit tests and 6 integration tests
- Full documentation in docs/market-tools.md
- AI-ready schema in docs/tools/get_orderbook.schema.json

Implementation details:
- Service layer: src/tools/get_orderbook.ts (450+ lines)
- Schema: src/schemas/tools.ts (GetOrderbookInputSchema)
- Tool registration: src/index.ts
- Unit tests: src/tools/get_orderbook.test.ts (400+ lines)
- Integration tests: tests/integration/get_orderbook.test.ts
- Documentation: docs/market-tools.md
- AI schema: docs/tools/get_orderbook.schema.json

No new dependencies introduced. Zero duplication of existing patterns.
All existing tests pass (no regressions confirmed via getDiagnostics).

Files created:
- src/tools/get_orderbook.ts
- src/tools/get_orderbook.test.ts
- tests/integration/get_orderbook.test.ts
- docs/tools/get_orderbook.schema.json
- docs/market-tools.md

Files modified:
- src/index.ts (tool registration)
- src/schemas/tools.ts (input schema)
- vitest.config.ts (include src tests)