feat: make keyboard shortcuts configurable

[hahhforest]

Summary

Adds configurable keyboard shortcuts for app actions exposed in Settings > Keyboard Shortcuts.

Why

Shortcut bindings are currently hard-coded, which makes conflicts with system, editor, or personal workflows hard to resolve.

What changed

• Added shared shortcut definitions, override normalization, platform-aware matching, display formatting, conflict detection, and Electron accelerator conversion.
• Added a Settings editor to record, clear, disable, and reset shortcuts by action category.
• Wired shortcut preferences through the main process, shell, navigator, menu accelerators, tooltips, and search/add-workspace shortcut hints.
• Ensured shortcut recording in Settings is not intercepted by the app-level shortcut listener.
• Added unit coverage for defaults, overrides, matching, recording, validation, conflicts, formatting, and accelerators.

Test plan

• npx --yes bun test packages/shared/src/keyboard-shortcuts.test.ts
• npx --yes bun run build
• git diff --check

[yiliush]

All contributors have signed the CLA ✍️ ✅
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[hahhforest]

I have read the Contributor License Agreement (CLA) and hereby sign the CLA.