perf(main): debounce synchronous file writes to reduce main thread blocking

[monotykamary]

Summary

Some quick wins to avoid that "freezing" feeling when opening the clipboard history on top of the other things. Adds write debouncing to reduce blocking I/O operations on the main thread during frequent clipboard and snippet operations.

Changes

Debounced Writes (100ms)

• clipboard-manager.ts: saveHistory() - batches clipboard history writes
• snippet-store.ts: saveToDisk() - batches snippet modification writes
• memory.ts: writeLocalMemories() - batches memory writes
• settings-store.ts:
  • Added saveSettingsAsync() for non-blocking settings writes
  • Debounced saveOAuthTokens() for OAuth token persistence

Directory Creation Optimization

• Moved fs.existsSync + mkdirSync calls from hot paths to startup:
  • clipboard-manager: ensureClipboardDirs() called once on monitor start
  • snippet-store: ensureSnippetsDir() called once on init

Impact

• Reduces main thread blocking during rapid copy operations
• Batches multiple quick edits into single disk writes
• Improves responsiveness during heavy clipboard/snippet usage

Testing

• TypeScript compilation passes
• All existing functionality preserved
• Debouncing only affects write timing, not behavior

[monotykamary]

Although logically sound (and not much to break here), there does need to be a performance harness for us to validate it instead of vibe testing it.

[shobhit99]

Although logically sound (and not much to break here), there does need to be a performance harness for us to validate it instead of vibe testing it.

I will look into performance testing tools today. will test these changes manually for now. Thanks!