refactor: move screen recording onto platform runtime

[thymikee]

Summary

• Route record through the request-bound platform runtime and the durable capture lifecycle while preserving the public CLI and response shape.
• Preserve exact-owner recovery, fencing, cancellation rollback, provider no-fallback, and platform-specific finalization across Android, Apple, HarmonyOS, and Web.
• Remove the retired recording backend/provider route, keep trace execution separate, and add the R16 command-atomic cutover gate.

Stacked on #1720. This layer touches 256 files, confined to the screen-recording command family and its shared durable-capture lifecycle.

Validation

• pnpm check:affected --run: 532 files / 4,518 tests passed; changed-line coverage 88.65%, changed-branch coverage 80.30%; provider progress 53/53 commands and 67/67 device-observable flags.
• Android helpers and iOS/macOS XCTest runner builds passed.
• Live iPhone 17 Pro simulator and Pixel 9 Pro XL emulator flows exercised public start/open/stop, daemon-loss cleanup, replacement start, and playable artifact finalization. ffprobe verified HEVC simulator MP4s and H.264 Android MP4s.
• Live verification exposed and closed exact process-identity regressions for simulator xcrun to simctl exec and Android missing/timeout-shaped /proc probes.

No CLI docs or skills changed because public command behavior is preserved; ADR 0019 and structural gates own the internal cutover.

[github-actions]

PR Preview Action v1.8.1
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[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	2.13 MB	2.17 MB	+31.7 kB
JS gzip	695.9 kB	708.6 kB	+12.7 kB
npm tarball	827.4 kB	836.3 kB	+8.9 kB
npm unpacked	2.88 MB	2.91 MB	+32.1 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	26.5 ms	26.3 ms	-0.2 ms
CLI --help	65.8 ms	65.6 ms	-0.2 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/dispatch.js	+41.4 kB	+12.9 kB
dist/src/runtime2.js	+25.3 kB	+7.6 kB
dist/src/internal/daemon.js	-2.8 kB	+840 B
dist/src/sdk-batch-runner.js	+1.2 kB	+356 B
dist/src/session.js	+1.7 kB	+330 B

[thymikee]

Not ready at exact 2db0a9b0:

• [P2] Linux/Vega record start now falls through narrowDeviceBinding and reports the internal Runtime operation screenRecordingStart is unavailable with no hint, replacing the prior operator-facing record is not supported on this device. Give the screen-recording unavailability fact/handler a record-specific public message and recovery hint, with a production-route regression.
• [P2] src/daemon/handlers/__tests__/record-runtime.test.ts is a new 549-line file. AGENTS.md requires extraction above 500 LOC and explicitly says tests are not exempt. Split start from stop/recovery and move the shared runtime harness to a sibling fixture.
• ADR 0019 says future command units must define and review their own cumulative package budget rather than inherit checkpoint headroom. This unit adds +31.7 kB raw JS, +12.7 kB gzip, +8.9 kB tarball, and +32.1 kB unpacked versus refactor: extract durable capture resource lifecycle #1720, but the PR/ADR records no reviewed recording-unit budget. Reconcile and document that acceptance before readiness; the green per-PR Size job does not make the decision.
• Practical evidence covers iOS simulator and Android emulator only in summary prose. This cutover changes Apple/macOS, Android, HarmonyOS, Web and provider recording routes. Attach exact-head command/output evidence with artifact/playability, recovery/replacement-start and session cleanup; run the other available changed routes, and explicitly record unavailable HarmonyOS hardware as residual risk.

All exact-head CI checks are green and the architectural cutover otherwise traces coherently. PR is stacked on draft #1720. Do not label ready.