Add mobile Safari (iPadOS) version of the browser feedback extension

[selfcontained]

Summary

Ports the Dispatch browser feedback extension (#783) to mobile Safari so page feedback can be sent to agents while testing on an iPad. Same server-side pairing/token/submission system — zero server changes — with a mobile-first client flow.

How it works on iPad

1. Tap the Dispatch extension in Safari's toolbar → popup handles connect/pairing (first run) or a single Select element button.
2. Everything else happens in a transient in-page overlay: tap an element (page clicks are blocked while aiming, scrolling still works), refine with ‹ Parent / Child › toolbar buttons, confirm, then a bottom-sheet card (agent picker + comment + Send) that releases page input. On send/cancel every injected node is removed.
3. Pairing survives the popup being dismissed: the background script owns the poll loop and persists the pending pairing, so reopening the popup after approving in Dispatch completes the connection.

Implementation

• Shared core extraction: worker-core.ts (fetch/auth/pairing/submission handling) pulled out of the Chrome service worker, which is now a thin shell — Chrome behavior unchanged. extension-api.ts (browser ?? chrome) is the entire Safari compat layer.
• Safari background (src/safari/): pairing-session.ts (persisted, resumable poll; cancel-after-late-approval disconnects), overlay-session.ts (activeTab-based injection with ready-probe retries, tab lifecycle cleanup).
• Overlay (src/safari/overlay/): pointer-event tap detection tuned for touch, pure refine.ts parent/child trail, shadow-DOM card, visualViewport math for pinch-zoom/keyboard, idempotent retry via stable clientSubmissionId.
• Build: pnpm --filter @dispatch/browser-extension build:safari → dist/safari/unpacked (popup, classic-script background, overlay IIFE, Safari manifest). Chrome zip pipeline untouched.
• Xcode project checked in at apps/browser-extension/safari/ (converter shell, references the dist directly); TestFlight/simulator steps in the README. MARKETING_VERSION sync is test-enforced.
• Web settings: Chrome / "Safari on iPad" toggle in the install guide.
• Drive-by: Chrome manifest.json version was stale (0.28.4 vs package 0.29.0) — fixed; the sync test now passes again.

Testing

• 97 unit tests (extension) incl. new pairing-session (fake timers), popup reducer, refine, viewport, manifest/pbxproj version sync.
• New Playwright harness (e2e/browser-extension-overlay.spec.ts) drives the built overlay bundle headlessly with a touch context and stubbed extension bridge: tap → refine → card → failed send → retried send with the same clientSubmissionId → teardown.
• Full suite: pnpm run check, pnpm run test, pnpm run finalize:web, pnpm run test:e2e (184 passed after fixing the pairing-copy assertion).
• iPad Pro 11" simulator: app builds, installs, launches; Safari manifest + all bundle files verified inside the built .appex.

Needs a human (can't be automated)

• Set your Team in Xcode signing, archive, upload to App Store Connect, install via TestFlight.
• On-device validation of touch picking, keyboard/pinch-zoom behavior, and the per-site access grant flow (top open risk: whether permissions.request prompts for the Dispatch origin on iPadOS — the fallback guidance paths are built in).

🤖 Generated with Claude Code

[selfcontained]

Full end-to-end validation on iPad Pro 13" simulator (driven via AXe HID automation):

1. ✅ Extension enabled in Settings → Apps → Safari → Extensions; All Websites → Allow
2. ✅ Toolbar button opens the popup; connect form → insecure-HTTP acknowledgement gate → "Connect anyway"
3. ✅ Verification tab opened (popup destroyed, as expected); approval card showed code in the web UI
4. ✅ Background pairing resume proven: Safari killed the background worker after the popup closed, so the poll died mid-pairing — reopening the popup completed the exchange in one call ("Browser connected to Dispatch.")
5. ✅ Paired browser listed as "Safari on iPadOS · 304A" (device-name heuristic correct in a worker context)
6. ✅ Select element → popup self-closes → in-page hint → tap highlights element → ‹ Parent / Child › refinement → Use ✓
7. ✅ Comment card loaded the real agent list (seeded theme polish agent) via the authenticated background fetch, typed a comment with the on-screen keyboard flow, Send
8. ✅ Submission persisted in browser_feedback_submissions with full comment + element context; card surfaced Prompt delivery failed. with the comment preserved for retry (expected — the seeded demo agent has no real process behind it)

Remaining human steps are unchanged: TestFlight signing/upload and real-device touch/pinch-zoom feel.