feat(route-engine): harden transport mode generation

[kubohiroya]

Summary

• enforce routeMode-aware route engine capability validation for generated route requests
• make OSRM generation options explicit and fail-fast instead of defaulting profile/geometries/overview
• share route MVT source-layer/promoteId constants across geometry artifacts, preview, and folder map rendering
• document RouteDB.tileIndex as nearest-search/legacy cleanup only, not canonical tile lineage

Issues

• Closes feat(route-engine): route mode ごとの長距離 geometry generation を完成させる #1510
• Closes refactor(route-mvt): MVT-first rendering・LOD・lineage 契約を全 route mode で検証する #1511

Verification

• pnpm install -> exit 0 (existing gen-iso3166-2 bin warnings)
• pnpm exec biome check --write <touched source files> -> exit 0
• pnpm -w turbo run typecheck --filter @hierarchidb/route-api --filter @hierarchidb/route-engine --filter @hierarchidb/route-plugin --filter @hierarchidb/runtime-worker --filter @hierarchidb/app -> exit 0
• pnpm -w turbo run test --filter @hierarchidb/route-engine --filter @hierarchidb/route-plugin -> exit 0
• git diff --check -> exit 0

Rollback

• Revert this PR to restore the prior route generation and route MVT rendering contracts.
• Existing persisted MVT artifacts remain derived data and can be regenerated per node.

[kubohiroya]

Reviewed the PR diff for route engine capability enforcement, OSRM option strictness, route MVT layer constants, tileIndex usage comments, and matching spec/test updates. No blocking issues found.

Local verification before PR:

• pnpm exec biome check --write -> exit 0
• pnpm -w turbo run typecheck --filter @hierarchidb/route-api --filter @hierarchidb/route-engine --filter @hierarchidb/route-plugin --filter @hierarchidb/runtime-worker --filter @hierarchidb/app -> exit 0
• pnpm -w turbo run test --filter @hierarchidb/route-engine --filter @hierarchidb/route-plugin -> exit 0
• git diff --check -> exit 0