Order tiles by recent app usage (opt-in)

[peterp]

New setting: "Order tiles by recent app usage" (default off).

When on, tiles in the overlay are sorted with most-recently-activated apps first. Saved per-display drag order is used only as a tiebreak.

• Recorded via `NSWorkspace.didActivateApplicationNotification` plus the previously-frontmost app at `show()`
• Stored in `UserDefaults` key `appUsageOrder` (capped at 128 entries)
• Keyed by bundle identifier (with `pid:N` fallback) so the rank is stable across windows of the same app
• Skips cmdcmd itself and non-`.regular` apps
• Off by default — preserves the existing drag-to-reorder behavior. Turning it on overrides drag order across sessions; an inline note in Settings calls this out.

Credit to @plyght — adapted from #1.

Test plan

• `./build-app.sh && open cmdcmd.app`
• Default off → tiles preserve drag-to-reorder as before
• Turn on → switch through several apps → ⌘⌘ → most recent apps appear first
• Drag-reorder while on → in-session works visually, but next show reverts to usage order
• Switch off → next show falls back to saved drag-order
• Setting persists across restarts

🤖 Generated with Claude Code