Add route_request dispatch coverage

[ChristianPavilonis]

Summary

• Add focused Fastly adapter route_request dispatch coverage.
• Cover static TSJS success and unknown bundle handling.
• Cover public discovery and unauthenticated admin dispatch.
• Cover auction dispatch through consent-dependent setup.
• Cover unknown-route publisher fallback dispatch without configured consent persistence.

Closes #451

Tests

• cargo test -p trusted-server-adapter-fastly route_tests -- --nocapture
• cargo fmt --all -- --check
• cargo test --workspace
• cargo clippy --workspace --all-targets --all-features -- -D warnings