Release 1.4.0

Fixes:
- Sandbox: add LaunchAgent temporary-exception entitlement
- Mirror URL: fix broken buildMirrorURL (URLComponents with ; separator)
- Cleanup: add bounds check to prevent crash on missing source
- State safety: pass MirrorConfig instead of mutating global @State
- KVC: remove misleading do-catch around setValue:forKey:
- Log cap: limit in-memory log to 2000 lines
- CLI: fix race with calendar loading
- launchCtl: separate stdout/stderr pipes

Features:
- Cancel button for long-running mirrors
- Progress indicator for multi-route runs (Route X of Y)
- Target event cache across routes

Code quality:
- Extract BlockMath, MirrorUtils, EventFilters, MirrorConfig
- Add 45 unit tests across 3 test files
- Refactor mergeGapMin to computed property
- Make log editor read-only

Build:
- Bump version to 1.4.0 (build 18)
- Add LSMinimumSystemVersion 15.5

BusyMirror/Info.plist

@@ -4,6 +4,8 @@
 <dict>
 	<key>LSUIElement</key>
 	<true/>
+	<key>LSMinimumSystemVersion</key>
+	<string>15.5</string>
 	<key>NSCalendarsFullAccessUsageDescription</key>
 	<string>BusyMirror needs access to your calendars to create busy placeholders.</string>
 	<key>NSRemindersFullAccessUsageDescription</key>