fix: Release the Frame Output thread on dispose and unmount

[chocky335]

What

On Android, each frame output keeps its com.margelo.camera.frame thread after the camera closes, so every camera mount leaks one thread.

How

HybridFrameOutput and HybridDepthFrameOutput now shut their executor down in dispose(). useFrameOutput disposes its output on unmount or replacement, one microtask late so a StrictMode effect re-run keeps it alive.

Review focus: the hook disposes the output while <Camera> may still have it configured until its teardown configure([]) runs.

The thread test comes from #4212 by @dmandrade. It stays red on iOS until HybridNativeThread.swift rejects work after dispose. I can follow up with that, and with the same unmount dispose in useDepthOutput.

Closes #4213

Related Pull Requests

• test: frame output thread keeps accepting work after dispose() #4212: test only, included here
• fix: Clear native output callbacks in output hooks on unmount #4192: clears hook callbacks on unmount, overlaps in useFrameOutput.ts (merges cleanly) and conflicts in visioncamera.hooks.harness.tsx

[chocky335]

Thread count on a Pixel 8 Pro, from adb shell ps -T -p <pid> sampled about every 2 s, over 10 mount and unmount cycles of <Camera outputs={[useFrameOutput(...)]}> and then a 25 s hold.

Build	During the cycles	After 10 cycles
Before	rises from 1 to 10	10 (16 samples)
After	0 or 1	0 (17 samples)

Harness runs on the same device: both new tests fail on the baseline APK and pass with the fix (hooks and frame suites, 19 passed, 3 skipped). The two camera-view failures (initial zoom, initial torch) fail on the baseline too.

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