## Why
Another process sharing `CODEX_HOME` can replace an installed plugin version
without invalidating the current process's caches. This could leave skill
listings tied to stale plugin paths and retain obsolete plugin generations.
## What changed
- Reject cached plugin loads when their roots no longer match the active
installation, so skills are reloaded after upgrades or rollbacks.
- Keep the 32 most recently used configuration-based skill snapshots while
allowing callers to continue using snapshots that have been evicted.
## Testing
- Cover external plugin upgrades and rollbacks through `skills/list`, including
a subsequent warm-cache read.
- Cover cache eviction, reuse, and the lifetime of caller-held snapshots.
GitOrigin-RevId: ca00f9539c01461e3945d340bf63f8436665220b
50fffd5ed3