feat: add profile export command

[kacper-mikolajczak]

Summary

• Adds profile export <file> CLI command that exports profiling data in React DevTools Profiler JSON format (version 5)
• The exported file can be imported directly into React DevTools browser extension via the Profiler tab's import button
• Maps internal ProfilingSession data to the ProfilingDataExport schema: commits, fiber durations, change descriptions, and component tree snapshots

Usage

agent-react-devtools profile start
# ... interact with app ...
agent-react-devtools profile stop
agent-react-devtools profile export profiling-data.json

Then open React DevTools Profiler tab and click the import button to load the JSON file.

What's included in the export

Field	Source	Notes
commitData	ProfilingSession.commits	Full mapping including durations, change descriptions
snapshots	ComponentTree nodes	Current tree state at time of export
initialTreeBaseDurations	First commit's fiberSelfDurations	Approximation - exact base durations not tracked
operations	Empty arrays	Not captured during profiling; flamegraph/ranked still work
effectDuration / passiveEffectDuration	null	Not available from the devtools protocol

Test plan

• 8 new unit tests covering: null cases, version format, commit mapping, change descriptions, snapshots, tree base durations, JSON serialization
• All 76 tests pass
• Manual: profile a real app, export, import into React DevTools Profiler tab

[changeset-bot]

🦋 Changeset detected

Latest commit: a4f339b

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
agent-react-devtools	Minor

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[kacper-mikolajczak]

CC @piotrski

[piotrski]

@codex review