feat(adapter-duffel): add Cars API (search → quote → book) v0.7.2

[telivity-otaip]

Summary

Duffel launched Cars as a full API vertical alongside Flights and Stays. This PR extends @otaip/adapter-duffel with the rental-car surface — same Bearer auth, same Duffel-Version: v2, just under the /cars/ namespace. Patterned identically to the Hotelbeds Activities/Transfers extension (#90): one adapter class, new product surface.

What's new on DuffelAdapter

Method	Endpoint
searchCars	POST /cars/search
quoteCar	POST /cars/quotes
bookCar	POST /cars/bookings
getCarBooking	GET /cars/bookings/{id}
cancelCarBooking	POST /cars/bookings/{id}/actions/cancel

Three-step flow (search → quote → book), unlike the two-step flight flow. Search is geo-coordinate based; the brief explicitly defers IATA-to-coordinate conversion (DQ-C8). The adapter accepts only { latitude, longitude, radius? } per location.

The shared request() helper now accepts an optional AbortSignal (pre-flight check; in-flight cancel needs an upstream change to fetchWithRetry, same caveat the Hotelbeds adapter carries).

Files

• New: cars-types.ts (canonical + wire types — CarRate, CarQuote, CarBookResponse, etc., plus a Money type), cars-mapper.ts (decimal.js-backed wire→canonical mapping), __tests__/cars.test.ts (18 cases), docs/knowledge-base/cars.md.
• Edit: duffel-adapter.ts (5 methods + request() signal threading), mock-duffel-adapter.ts (full three-step mock flow + 2 car fixtures), index.ts (re-exports), package.json (0.7.1 → 0.7.2).

Domain knowledge

docs/knowledge-base/cars.md captures the vendor brief verbatim and enumerates 8 open DOMAIN_QUESTION markers (DQ-C1..C8) for the gaps the brief leaves open:

• DQ-C1 — radius upper bound
• DQ-C2 — pickup_time / dropoff_time timezone
• DQ-C3 — car.category / car.type enum closure
• DQ-C4 — privacy_policies consent flow
• DQ-C5 — Card creation (explicitly out of scope)
• DQ-C6 — inbound_flight_number format (IATA vs ICAO)
• DQ-C7 — Refund computation on cancellation
• DQ-C8 — IATA-to-coordinate conversion (deferred per brief)

Per the constitution's no-invent rule, these are surfaced rather than guessed. The adapter falls back to the safe choice where it must (e.g. unknown payment_type → 'postpaid' so we never mis-charge) and documents the assumption inline.

Verification

• pnpm exec vitest run packages/adapters/duffel — 58 passed / 3 skipped (sandbox-gated).
• pnpm exec eslint packages/adapters/duffel/src — clean.
• pnpm --filter @otaip/adapter-duffel typecheck — clean.

Versioning

@otaip/adapter-duffel 0.7.1 → 0.7.2 (single-package patch bump per VERSIONING.md). The workspace-wide v0.7.2 release follows separately, same shape as #92 / #96. The brief asked for a "next minor" bump (0.8.0); flagging that we're sticking with the patch-bump policy unless you want to ratify another exception like the v0.7.0 hotelbeds case — let me know.

Out of scope (intentional)

• Card creation (POST /payments/cards) — separate Duffel API.
• IATA → coordinate conversion — DQ-C8.
• Refund amount computation — DQ-C7.
• Sandbox integration test — could land in a follow-up; the unit + mock surface validates the full happy path.

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