## Summary
- Preserve class names in the save-cache bundle so `@actions/cache`
error-name comparisons distinguish validation errors, benign
cache-reservation races, and finalization errors correctly.
- Add regression coverage that exercises the bundled `ValidationError`,
`ReserveCacheError`, and `FinalizeCacheError` constructors.
Fixes#1028
## Verification
- `npm run all` passed on Ubuntu 24.04 with Node 24.19.0: build, Biome,
packaging, and all 159 tests across 15 suites.
- `git diff --check` passed.
The save-cache bundle increases by about 77 KB raw (14 KB gzip) to
preserve the required names.
