Add fun visual-effect commands (Confetti, Fireworks, Snow, Rain) + expanded tray menu

[temperatio]

Summary

• Adds four native "fun" system commands modeled after Raycast's built-in Confetti extension: Confetti, Fireworks, Snow, and Rain. Each renders via a shared transparent, always-on-top overlay window helper (showFullScreenOverlayEffect) and shows up in the command palette like any other system command.
• Bursts stack instead of replacing one another — retriggering a command while a previous burst is still animating layers a new overlay window on top rather than closing the old one, matching Raycast's actual behavior.
• Expands the menu-bar tray menu with Extension Store..., SuperCmd Settings..., a Launch at Login checkbox, and Check for Updates... — previously it only had Open/Quit.
• Fixes an npm install failure on single-architecture Macs (e.g. Apple Silicon-only): @esbuild/darwin-x64 / @esbuild/darwin-arm64 were pinned as hard dependencies, causing EBADPLATFORM instead of being skipped like normal optional platform packages. Moved to optionalDependencies — the existing postinstall script already backfills whichever platform binary is missing for universal builds.

Details

• system-confetti: multi-burst rectangle particles tuned for wide screen coverage.
• system-fireworks: staggered rocket launches with trails that explode into radial showers.
• system-snow: continuously-recycled snowfall with sway, density scaled to screen size.
• system-rain: wind-angled streaks with ground splashes, same density scaling.
• Refactored the app-updater check/download/restart flow and the open-at-login apply+persist pairing into standalone functions (runAppUpdaterCheckAndInstall, setOpenAtLogin) so the new tray items and their existing IPC handlers share the same code instead of duplicating it.

Test plan

• npm run build:main / build:renderer / build:native all succeed
• Verified end-to-end with a Playwright _electron driver against an isolated --user-data-dir profile (never touched a real user profile): each command appears in the palette with correct title/icon, executing it spawns the real overlay window, and windows auto-close with no leaks
• Verified bursts stack (firing twice in quick succession keeps both overlay windows alive simultaneously)
• Verified the three new tray actions by calling the exact functions/IPC channels they invoke (setOpenAtLogin, system-open-extension-store, app-updater-check-and-install) — no crashes, expected results
• Packaged and manually installed an unsigned arm64 DMG locally to confirm the effects look right on a real display
• Manual review of visual density/timing tuning (subjective, may want further tweaks)