refactor: require Bun globally, add auto-install, remove Windows executable approach (#243)

- Delete BinaryManager.ts - no longer needed
- Simplify ProcessManager.ts - single Bun spawn path for all platforms
- Update smart-install.js - auto-install Bun if missing (Windows/Unix)
- Update documentation to reflect Bun requirement

This simplifies the codebase by:
- Using Bun consistently across all platforms (hooks + worker)
- Eliminating binary download/hosting complexity
- Zero native dependencies with bun:sqlite
- Auto-installing Bun on first run if not present

Co-authored-by: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -76,8 +76,8 @@ Settings are managed in `~/.claude-mem/settings.json`. The file is auto-created
 
 ## Requirements
 
-- **Bun** >= 1.0 (Mac/Linux runtime)
-- Node.js >= 18 (build tools)
+- **Bun** >= 1.0 (all platforms - auto-installed if missing)
+- Node.js >= 18 (build tools only)
 
 ## Quick Reference