fix(tippecanoe): remove --simplification=10 — distorts buildings at z18

Simplification with 10px tolerance makes rectangular buildings look
jagged/trapezoidal at high zoom. Without it, tippecanoe still simplifies
at lower zooms via --drop-densest-as-needed but preserves full geometry
at the base zoom (z18).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/rebuild-overview-tiles.sh

@@ -88,7 +88,6 @@ tippecanoe \
   --base-zoom=18 \
   --drop-densest-as-needed \
   --detect-shared-borders \
-  --simplification=10 \
   --no-tile-stats \
   --hilbert \
   --force