test(coverage): add tests for index/form events, raster, buildings, context
Push the Coverages namespace coverage up further:
* CoverageLive.Index — delete and recompute event handlers, the
in-progress flash branch, status_badge_class fallback. 35% → 87%.
* CoverageLive.Form — invalid-save round-trip, location_picked and
use_site_location event handlers. 61% → 77%.
* Coverages.Raster — query_rssi guard branches (not_ready, outside_bbox,
raster_missing, missing-bbox), cleanup no-op, and Lidar.Reader
parse_aaigrid header parsing. 63% → 75%.
* Coverages.Buildings — to_clutter height fallback, polygon coord
extraction, for_bbox PostGIS intersect against real DB rows. 43% → ~95%.
* Coverages context — topic helpers, subscribe + broadcast,
list_ready_for_organization, change_coverage, query_point happy and
empty paths, queue_compute idempotency. 65% → 93%.
Total project coverage 74.05% → 74.25%.