R-tree building, hex grid generation, and percentile sorting now run
off the main thread, eliminating 20s+ UI freezes on large datasets.
The old bundled HexgridHeatmap.js is replaced by a typed worker +
main-thread client with dual R-trees (worker for grid gen, main
thread for synchronous click queries).
The crawler subdirectory was the only active project. Moving it to the
repo root simplifies paths and removes the unnecessary nesting. The
vqa/ and immoweb/ directories were legacy/unused and have been removed.
Updated .drone.yml, .gitignore, .claude/ docs, and skills to reflect
the new flat structure.
