macOS: add menu-bar status item to the resident agent

[m31-galaxy]

Summary

Stacked on top of #23 (base branch: macos). Adds a menu-bar status item to the macOS resident background agent.

The resident agent runs as an accessory app (NSApplicationActivationPolicyAccessory, LSUIElement), so it has no Dock icon and previously offered no visible UI — casting was only possible via the global hot key or by relaunching the app. This adds a status item in the menu bar so the agent is discoverable and controllable.

Changes

• pkg/cocoa/cocoa.m
  • New HexStatusController with cast: (funnels through the existing request_show path — same as the hot key and relaunch) and quit: ([NSApp terminate:]) actions.
  • New cocoa_setup_menu_bar(): creates an NSStatusItem with a template SF Symbol glyph (wand.and.stars, matching the spell-casting metaphor; falls back to a ✦ title if unavailable) and a menu with Cast Gesture and Quit Hexecute. Idempotent; runs on the main thread.
  • cocoa_destroy() removes the status item.
• pkg/cocoa/cocoa.h — declares cocoa_setup_menu_bar.
• pkg/cocoa/cocoa.go — CocoaWindow.SetupMenuBar() wrapper (macOS-only; intentionally not part of the platform.Window interface).
• cmd/hexecute/run_darwin.go — calls window.SetupMenuBar() from runMain after the hot key registers.

Notes

• SF Symbols require macOS 11+, which matches LSMinimumSystemVersion (11.0) in Info.plist.
• The menu works under the agent's manually-pumped event loop: status-item clicks are dispatched via [NSApp sendEvent:] in cocoa_wait_for_show, which then drives the menu's own tracking loop.
• This was developed on a Linux host; the Cgo/Objective-C path is build-tagged darwin and could not be compiled locally. gofmt and the non-darwin go build ./... are clean. The macOS CI job (added in Add macOS support with native Cocoa overlay window #23) will compile and link it.

Verification (on macOS)

1. Build the .app and launch the resident agent (hexecute --background).
2. Confirm a wand glyph appears in the menu bar (right side).
3. Click it → Cast Gesture shows the overlay (same as the hot key); draw a gesture and confirm it executes.
4. Click it → Quit Hexecute exits the agent and the glyph disappears.
5. Confirm the global hot key and relaunch-to-cast still work unchanged.

🤖 Generated with Claude Code

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