feat: add CLI and scripting support

[karbassi]

Closes #51, closes #105.

Summary

• Add URL scheme (timer://) to control the timer programmatically — e.g. open "timer://5", open "timer://2:30?window=2"
• Add launch argument support — e.g. open -a Timer --args 5 --window 2
• Add AppleScript support via scripting definition (.sdef) — e.g. tell app "Timer" to start timer "5" window 2
• Add CLI wrapper (timer-cli) as a thin shell script over the URL scheme — e.g. ./timer-cli 5 -w 2

Commands

Command	Description
<duration>	Start timer (e.g. 5 = 5 min, 2.5 = 2m30s, 2:30 = 2m30s)
stop	Stop the timer (keeps time displayed)
reset	Stop and clear timer to zero
pause	Toggle pause/resume
new	Open a new timer window

All commands accept an optional window parameter (1-based) to target a specific timer when multiple windows are open.

Files changed

• Timer/AppDelegate.swift — URL handler, launch args parser, command router, time input parser
• Timer/MVClockView+Behavior.swift — startTimer(seconds:) method
• Timer/MVTimerController.swift — expose clockView for programmatic access
• Timer/Info.plist — URL scheme registration, AppleScript enabled
• Timer/Timer.sdef — scripting definition (start/stop/pause/reset/new)
• Timer/TimerScriptCommand.swift — NSScriptCommand subclass
• Timer.xcodeproj/project.pbxproj — add new files to target
• timer-cli — shell script CLI wrapper
• Makefile — install-cli target

Test plan

• make build — clean build, no errors
• make lint — 0 violations
• make test — all tests pass
• open "timer://5" — starts 5-minute timer
• open "timer://2.5" — starts 2m30s timer
• open "timer://2:30" — starts 2m30s timer
• open "timer://stop", open "timer://reset", open "timer://pause"
• open "timer://new" — opens new timer window
• open "timer://5?window=2" — targets second window
• open -a Timer --args 5 — starts via launch args
• AppleScript: tell application "Timer" to start timer "2"
• ./timer-cli 5 — starts via CLI wrapper