fix: keep iOS runner hot across app closes

[thymikee]

Summary

Keep the iOS simulator XCTest runner reusable across idle gaps, Maestro-style app closes, app relaunches, and local runner source/cache changes.

• adds a lightweight runner-side idle heartbeat so Xcode does not retire the long-lived XCTest process while it waits for commands
• keeps targeted app closes and open --relaunch from stopping the iOS simulator runner, so stopApp/relaunch does not force the next command to relaunch XCTest
• adds a simulator transport fallback for already-ready runner sessions when the direct localhost endpoint is temporarily unavailable
• splits the runner connect retry path into primary endpoint, ready-simulator fallback, and refreshed device-tunnel phases so the retry logic remains auditable
• suppresses stale-snapshot node-count warnings when switching between different snapshot presentation modes, such as full tree to compact interactive
• adds a bounded compact-interactive snapshot path for apps where XCTest cannot enumerate the normal accessibility root, avoiding expensive app/window/root probes and returning quickly with available refs or an explicitly warned sparse snapshot
• documents the iOS snapshot backend strategy in docs/adr/0004-ios-snapshot-backend-strategy.md: full recursive XCTest snapshots remain the rich diagnostic path, compact interactive snapshots are the bounded agent-facing path, and Bluesky-class semantic coverage needs a future simulator AX-service backend rather than more XCTest retries
• restarts a live iOS runner when the expected xctestrun artifact path changes, preventing local dirty-source/cache changes from continuing to serve an old runner process
• makes alert handling prefer blocking SpringBoard modals and fail honestly if the chosen alert button does not actually dismiss the alert

Root Cause

The slow/empty snapshot -i -c behavior came from two separate issues:

• PR fix: preserve iOS AX snapshot failures #639 correctly started preserving XCTest AX serialization failures instead of swallowing them as empty snapshots. That exposed real apps whose simulator accessibility tree can fail under XCTest with kAXErrorIllegalArgument.
• The first compact fallback still read app/window/root properties before flat enumeration. On broken trees those reads can hit the same expensive XCTest AX path, so compact snapshots could become much slower than plain snapshots.

This PR now treats compact interactive snapshots as their own bounded strategy. It does not pretend XCTest can semantically inspect every app. When XCTest typed queries cannot enumerate controls either, the CLI returns a fast sparse snapshot with a warning. A complete semantic fix for those apps should be a simulator AX-service backend normalized into the existing SnapshotNode model.

Validation

• pnpm exec vitest run src/platforms/ios/__tests__/runner-session.test.ts
• pnpm exec vitest run src/__tests__/runtime-snapshot.test.ts
• pnpm check:fallow
• pnpm check:quick
• pnpm build
• pnpm build:xcuitest:ios
• Local iPhone 17 Pro / Settings: cached prepare ios-runner 4.7s from fresh state; snapshot -i -c 1.46s with visible Settings refs.
• Local iPhone 17 Pro / Bluesky logged-in state: reproduced XCTest kAXErrorIllegalArgument sparse-tree behavior; optimized snapshot -i -c returns bounded sparse output in 0.64s instead of spending ~10-60s on root/window/app probes and runner restarts.
• Local iPhone 17 Pro / React Navigation example: compact snapshot returned useful refs; first snapshot 5.69s while app settled, repeated steady-state snapshot 0.98s.

[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	1.1 MB	1.1 MB	+2.4 kB
JS gzip	370.5 kB	371.1 kB	+651 B
npm tarball	476.9 kB	479.4 kB	+2.5 kB
npm unpacked	1.6 MB	1.6 MB	+12.3 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	22.1 ms	21.8 ms	-0.4 ms
CLI --help	34.2 ms	33.5 ms	-0.8 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/2415.js	+1.7 kB	+407 B
dist/src/9533.js	+660 B	+215 B
dist/src/session.js	+26 B	+29 B