Scope diff patch cache key by theme

- pass a cache scope into `getRenderablePatch` and include resolved theme in DiffPanel cache keys
- add a test proving `buildPatchCacheKey` changes when cache scope changes
8a567ba3d5Julius Marminge committed on 2/27/2026, 1:38:19 AMparent5748a99
2 files changedLine totals unavailable