feat: add doctor command

[thymikee]

Summary

Add a read-only doctor command for RN/Expo/Metro preflight checks, with progressive human output and JSON evidence.

Closes #874

Validation

Verified with focused unit coverage for CLI parsing/output/progress, provider-backed doctor scenarios, Apple device ordering tests, static type/lint checks, build, and live CLI smoke for devices/doctor selection.

[github-actions]

Size Report

Metric	Base	Current	Diff
JS raw	1.3 MB	1.4 MB	+12.4 kB
JS gzip	436.5 kB	440.7 kB	+4.2 kB
npm tarball	574.4 kB	578.9 kB	+4.5 kB
npm unpacked	1.9 MB	2.0 MB	+12.6 kB

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	26.0 ms	26.2 ms	+0.2 ms
CLI --help	46.1 ms	45.8 ms	-0.3 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/session.js	+9.0 kB	+3.0 kB
dist/src/2948.js	+2.0 kB	+683 B
dist/src/9919.js	+327 B	+84 B
dist/src/cli-help.js	+168 B	+46 B
dist/src/cli.js	+51 B	+21 B

[thymikee]

I do not see a routing blocker in the doctor command path: the command facet projects through the daemon registry, and the Android probes still run under the request-scoped provider path via the adb executor scope.

One thing I would address before merge: src/daemon/handlers/session-doctor.ts lands as a 571-line handler and mixes option parsing, session/device selection, app discovery, Android foreground/reverse/animation probes, RN overlay checks, Metro probing, output ordering, and progress emission. The repo agent guide asks us to extract focused submodules once implementation files grow past 500 LOC. Please split the probe families out before merge, for example keeping session-doctor.ts as the orchestrator and moving Android/Metro/RN checks into focused session-doctor-* modules or a small doctor-checks/ group. That will make follow-up doctor checks reviewable without growing the handler further.

[thymikee]

Re-check after the latest push: this still needs the split before I would call it merge-ready. src/daemon/handlers/session-doctor.ts is now 599 LOC, and the Android/Metro/RN/session/device checks are still all in that handler. CI is green and the route/provider coverage looks fine, but the previous maintainability finding is unresolved.

[thymikee]

GitHub now reports this branch as conflicted against main after #884 merged. Please rebase, resolve the conflicts, and reply with what changed plus any validation you reran. I am holding re-review until the branch is clean again.