feat(api): implement Phase 20 HTTP API with OpenAPI and Swagger

[404khai]

What changes

Roadrunner's routing, dispatch and shared operational state were only available through libraries and the CLI. Phase 20 adds a roadrunner-api Axum/Tokio server with generated OpenAPI 3.1 and vendored Swagger UI at /swagger-ui/.

• Expose all specified route/order/rider/dispatch/delivery/simulation endpoints, plus the approved operational queries, fleet/recovery/cancellation commands, readiness/forecast/traffic updates and observed action lifecycle.
• Keep one volatile operational authority and publication lane. Assemble server contexts, evaluate outside the writer, certify exact static-road temporal applicability, then publish effects and terminal command recognition together.
• Bind bearer credentials to stable principals/capabilities/resource scopes and observation sources. Require namespace-qualified intent and principal-scoped idempotency keys; preserve original outcomes across retries and lost responses.
• Return directed segment GeoJSON, explicit graph/profile/objective/traffic identity, opaque order/rider references and recorded decision/publication evidence. Run simulations in a separate authority.
• Add run/contracts documentation, controlled race/disconnect tests, and a reproducible loopback HTTP benchmark with raw measurements and hardware/dataset/build/configuration details.

For example, creating an order leaves it unassigned; POST /v1/dispatch evaluates and attempts an authentic publication. Repeating the same key returns that original outcome, while conflicting meaning returns 409. A state change or expiry during evaluation rejects the proposal wholly.

Validation

• cargo fmt --all -- --check
• cargo +1.99.0 clippy --workspace --all-targets --all-features --locked -- -D warnings
• cargo +1.99.0 test --workspace --all-features --locked: 233 passed; the existing opt-in benchmark remains ignored.
• Release API build, OpenAPI export/component-reference checks, vendored Swagger HTTP test and native browser inspection.
• python3 scripts/collect_http_api_benchmark.py: 30 raw samples per workload on the verified 58-node/114-edge fixture; retries/effect counts verified.

See docs/phase-20-completion.md and docs/evidence/phase-20-verification.json for evidence and scope.

Boundaries

The binary requires explicit trusted-local mode, a bearer credential and a loopback bind. Embedded hosts provision actual observation trust. Recognition is volatile and single-process; discarded namespace outcomes are unknown. Operational certification supports free flow/static traffic and retains the existing unknown-prefix/time-dependent proof limits. Persistence, fencing, durable recovery, outbox/inbox and broker delivery remain Phases 21/22. The tiny loopback benchmark is an adapter baseline, not a scalability or SLO claim.