fix(windows): reduce hook callback latency to prevent mouse drag lag

[debugtheworldbot]

Problem

Users report mouse drag becoming unresponsive/laggy after using KeyStats for a while on Windows 11 with high polling-rate mice (e.g. Razer DeathAdder V3).

Root Cause

ActiveWindowManager.GetActiveAppInfo() can be expensive on cache miss — it calls Process.GetProcessById() + FileVersionInfo which involve cross-process queries and disk IO. Windows enforces a strict timeout (~200ms) on WH_MOUSE_LL low-level hook callbacks; exceeding it causes Windows to skip or uninstall the hook, resulting in mouse drag lag.

Fix

Two changes, both in the hook's hot path:

1. InputMonitorService.cs — Keep GetActiveAppInfo() synchronous in the hook (for correct app attribution), but defer event dispatch (Invoke) to ThreadPool.

2. ActiveWindowManager.cs — Add a process-level cache (_processCache) by process ID, so BuildAppInfo() skips Process.GetProcessById + FileVersionInfo for already-seen processes. Combined with the existing window-handle cache, most hook calls now resolve via fast dictionary lookups with no cross-process overhead.

Changed Files

• KeyStats.Windows/KeyStats/Services/InputMonitorService.cs
• KeyStats.Windows/KeyStats/Helpers/ActiveWindowManager.cs

[gemini-code-assist]

Code Review

This pull request implements a process information cache in ActiveWindowManager to minimize expensive lookups during window switches and refactors InputMonitorService for clarity. A review comment suggests improving the cache eviction logic by removing the oldest entry rather than clearing the entire cache to maintain consistent performance.

[gemini-code-assist]

The current cache eviction strategy of clearing the entire cache is suboptimal. When the cache is full, this causes a performance spike as all cached items are lost and need to be recreated. A better approach is to evict only one item. Assuming a modern .NET runtime where Dictionary<TKey, TValue> preserves insertion order, you can remove the oldest entry by removing the first key.

                _processCache.Remove(_processCache.Keys.First());