refactor(react-native): collocate Metro, companion, and DevTools

[thymikee]

Summary

Collocate Metro preparation and session bindings, companion lifecycle and worker, and React inspection/profiling in private @agent-device/react-native.

One "." export points to src/index.ts. Its explicit, typed interface exposes Metro operations, session lifecycle operations, and runReactDevtools; runtime implementations load lazily. Persistence helpers and internal modules stay private. Public CLI and SDK behavior is preserved.

flowchart LR
  Adapters[CLI / SDK adapters] --> Entry[react-native index.ts]
  Entry --> Metro[Metro preparation and bindings]
  Entry --> Companion[Companion lifecycle and worker]
  Entry --> DevTools[React inspection and profiling]
  DevTools --> Metro
  Metro --> Companion

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82 files touched, mostly moves. Companion protocol/lifecycle code sits beside its worker; package-wide tests exercise the root interface, SDK session tests sit with the SDK, and shared fixtures live in test-kit. Remove the obsolete root overlay re-export; retain its canonical capture-kit implementation. Update ADR 0019 and path-keyed checks.

Validation

Tested commit: 143c6deee769c72ce19b818ece338006ef518c00.

• 1,194 focused tests and 39 overlay/command tests pass.
• pnpm check:affected --run: all runnable checks passed; 1,845 files / 15,564 tests passed, one skipped.
• Bundled CLI text/JSON and installed-package companion checks pass.
• Depgraph: all external package edges target src/index.ts; no root imports, value cycles, or zone cycles.
• Independent review at b60d2b2: no actionable findings; follow-up changes only a doc comment.
• CI integration and coverage pending on this head.

[github-actions]

Size Report

Metric	Base	Current	Diff
Installed (including dependencies)	5.29 MB	5.29 MB	+3.3 kB
Package (unpacked)	5.29 MB	5.29 MB	+3.3 kB
Package (download)	1.59 MB	1.59 MB	+1.2 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	23.3 ms	22.6 ms	-0.7 ms
CLI --help	63.3 ms	61.3 ms	-2.0 ms

[github-actions]

PR Preview Action v1.8.1
Preview removed because the pull request was closed.
2026-10-16 12:00 UTC

[cubic-dev-ai]

No issues found across 76 files

_{View guided diff | Turn on auto-fix | Re-trigger cubic}

[thymikee]

This PR is ready at b60d2b2. All 38 checks pass, and there are no conflicts. I did not build the package, so bundled chunk placement and d.ts inlining for the ./metro subpath rest on the passing packaging checks and your installed-package companion check. I checked test preservation by name and spot reads, not line by line. Not blocking, and fine to take or leave: the doc comment at https://github.com/callstack/agent-device/blob/b60d2b2/packages/contracts/src/companion-tunnel-scope.ts#L6 still names the old client/client-companion-tunnel-contract.ts path, so it could point at the companion folder in @agent-device/react-native; the session-binding helpers in https://github.com/callstack/agent-device/blob/b60d2b2/packages/react-native/src/index.ts#L75 are now async wrappers over a dynamic import, and a static export would keep them synchronous; bindingPath in https://github.com/callstack/agent-device/blob/b60d2b2/packages/test-kit/src/metro-session.fixtures.ts#L8 repeats the production hints path rule, which is acceptable, or the test could assert through readMetroSessionRuntime; and dropping the overlay re-export in https://github.com/callstack/agent-device/blob/b60d2b2/src/commands/react-native/index.ts#L58 is an unrelated cleanup that the PR body already mentions.

[thymikee]

Addressed the stale ownership comment in 143c6de: it now names @agent-device/react-native and drops the old migration history.

Kept the other choices deliberately:

• The lazy session wrappers keep the single entry within its startup budget. Using the repository's graph walker against the current source, the entry evaluates 6 modules; a static-export variant evaluates 25, above the 20-module ceiling. Every production caller awaits the facade methods.
• The independent fixture reader verifies persisted controlBaseUrl and deviceBaseUrls, including cleanup. readMetroSessionRuntime returns only the resolved control runtime, so substituting it would lose that persistence coverage. Raw storage helpers remain private to the package.
• The overlay change removes a redundant re-export during the requested related-code cleanup. Its canonical capture-kit implementation is unchanged, and the PR body names the deletion.

Executable code is unchanged from b60d2b2. pnpm check:affected --run passes at 143c6de (15,564 tests passed; one skipped).