chore: limit Cesium building tile cache

[rotwurstesser]

Description

Limit the Cesium Swissbuildings3D tile cache to 256 MiB with 128 MiB overflow. This bounds retained building tile content without changing screen-space error or active rendering detail. Other Cesium tilesets keep their defaults.

Benchmark

• Paired the deployed PR against the same build with Cesium's 512/512 MiB defaults restored at runtime
• Covered 16 locations, repeated nationwide eviction/revisit passes, rapid combined navigation, seeded random navigation, and building-layer recreation
• Peak building-tile payload: 255.99 MiB capped versus 511.97 MiB control (50% lower)
• Screen-space error stayed at 10; 95/96 paired location checkpoints had identical selected building triangles and draw commands
• The remaining checkpoint was a non-reproduced camera landing issue; a focused follow-up passed 60/60 landings with each cache setting
• No Cesium render errors, page exceptions, browser crashes, WebGL context losses, or unhandled rejections
• Mapviewer unit tests: 334 passed, 3 skipped; ESLint and existing CI pass

This verifies the Cesium building-tile payload reduction and functional equivalence for the tested scenarios. It does not claim a 50% reduction in total browser RSS.

Test link

Test link

[cypress]

web-mapviewer    Run #6617

Run Properties:   Passed #6617  •  227266d5f5: chore: limit Cesium building tile cache

Project	web-mapviewer
Branch Review	chore-limit-cesium-building-cache
Run status	Passed #6617
Run duration	04m 58s
Commit	227266d5f5: chore: limit Cesium building tile cache
Committer	Raphi
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	19
Skipped	0
Passing	222
View all changes introduced in this branch ↗︎