- Export `resolveCompletionCachePath` and `completionCacheExists` for external use
- Update `installCompletion` to require cache existence (never use slow dynamic pattern)
- Add `usesSlowDynamicCompletion` to detect old `source <(...)` patterns
- Add `getShellProfilePath` helper for consistent profile path resolution
- Update `formatCompletionSourceLine` to always use cached file