Add ID index functionality for efficient feature lookup by OSM ID

[JeremyBYU]

Description of Work

Adds efficient feature lookup by OSM ID using pre-built index files (*-indexes/ directory generated by geodesk-gol). Avoids full tile scans by narrowing search to the specific tile containing the feature.

What Changed

• New IdIndex class (src/feature/IdIndex.cpp, include/geodesk/feature/IdIndex.h) - Loads and queries index files, maps pile numbers to tile pointers, scans R-tree for matching IDs
• Public API on FeaturesBase - Added byId(id) method: nodes.byId(123), ways.byId(456), relations.byId(789)
• FeatureStore integration - Lazy-loads IdIndex on first use
• Example program (examples/query-id/)
• IndexFile fix - Minor adjustment in clarisma/store/IndexFile.cpp

Amount of Risk

Targeted change, low risk.

• Additive only - no modifications to existing query paths
• Graceful fallback - if index files are missing, byId() returns null
• Self-contained - new code isolated in IdIndex class

Future Work

• Update geodesk-gol to expose ID lookup in its query language, enabling syntax like w[id=12345] or /w12345 or a dedicated byId() function. Wanted to get your opinion on best way to handle that.

[cla-assistant]

All committers have signed the CLA.