docs(dispatch): close out Phase 13 with runnable example

[404khai]

Phase 13 Basic Dispatch was already implemented during the architecture remediation. This closes out the phase with usage documentation, a requirement-to-evidence completion report, and a runnable example that reuses the existing routing, evaluation, commit, and execution APIs.

The synthetic example demonstrates exhaustive road-ETA selection versus a bounded spatial shortlist, emits structured decision JSON, and executes the selected plan through pickup and delivery with custody and remaining-work assertions. The specification and architecture now record Phase 13 completion.

Validation:

• cargo fmt --all --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace — 96 tests pass; doc tests pass
• cargo run -p roadrunner-dispatch --example basic_dispatch — assertions pass and JSON parses
• Documentation file links resolve; git diff --check passes