Eliminates the silent-failure pattern where a route/activity row could
be committed with gpx IS NOT NULL but geom IS NULL if the PostGIS write
failed after the row insert.
- New gpx-save.server.ts owns all GPX validation (GpxValidationError,
validateGpx) and PostGIS geometry writes (writeGeom, tx-aware)
- createRoute, updateRoute, createActivity, createRouteFromActivity all
wrapped in db.transaction() covering row + geom + version snapshot
- demo-bot uses createRoute/createActivity instead of raw inserts;
errors propagate loudly
- Callback endpoint returns 400 for GpxValidationError instead of 401
- ADR-0006 documents the invariant for future explorers
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
