Harden production iOS pairing recovery

[BunsDev]

Summary

• add a fixed-input native Tailscale launcher for production macOS and Windows builds
• add shared Open Tailscale, Install Tailscale, and Retry recovery controls to both phone-pairing entry points
• retry signed invite generation with bounded backoff while keeping unusable QR codes hidden
• cover the recovery contract in TypeScript and Rust tests and document the production flow

Verification

• pnpm typecheck
• pnpm lint
• pnpm test:app
• pnpm test:api
• pnpm check:tests-wired
• pnpm test:mobile
• cd src-tauri && cargo check --lib

Bead: cave-9vcfw

[Copilot]

Pull request overview

This PR hardens the iOS phone-pairing recovery path when Tailscale is offline by adding a fixed-input native Tailscale launcher in the packaged desktop app and reusing shared recovery UI controls across pairing entry points, with bounded retry/backoff and supporting tests/docs.

Changes:

• Add shared pairing recovery helpers (failure classification + bounded retry) and a reusable TailscaleRecoveryActions UI component.
• Register a fixed-argument native open_tailscale_app Tauri command for macOS/Windows (with Linux returning a manual-action error).
• Extend coverage and docs: TS unit tests + Rust source-guard test + wiring into the test suite list + updated mobile Tailscale doc.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lib/tailscale-recovery.ts	Adds recovery attempt parsing, failure-kind classification, native launch wrapper, and bounded retry helper.
src/lib/tailscale-recovery.test.ts	Unit tests for native launch invocation and bounded retry behavior.
src/components/tailscale-recovery-actions.tsx	New shared UI actions (Open/Install/Retry) with announcer feedback and inline launch error display.
src/components/settings-phone.tsx	Replaces local Retry buttons with TailscaleRecoveryActions; adjusts reconcile return type to pass structured attempt results through.
src/components/mobile-handoff-modal.tsx	Makes start() consistently return a response object and adds TailscaleRecoveryActions to the error state.
src/components/mobile-handoff.test.ts	Asserts that both pairing entry points include recovery actions and that recovery uses the fixed native command + bounded delays.
src-tauri/src/shell_open_commands.rs	Implements open_tailscale_app with fixed native launch behavior per platform.
src-tauri/src/shell_open_tests.rs	Adds source-level guard assertions for fixed/parameterless Tailscale launcher wiring.
src-tauri/src/lib.rs	Imports open_tailscale_app for command registration on desktop builds.
src-tauri/src/tauri_setup.rs	Registers open_tailscale_app in the Tauri invoke handler list.
scripts/run-tests.mjs	Wires the new TS test file into the suite list (keeps check:tests-wired happy).
docs/mobile-tailscale.md	Documents the production recovery flow and UX behavior (hide unusable QR; bounded retries).

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