Fix extension test process leaks - #2856

Summary

• Stub adb logcat in Android platform tests so host tests do not launch real adb processes.
• Stub Edge spawning in the Expo web test so tests do not open a real browser.
• Clean up extension-owned LogCat monitors after Android tests and when the test runner exits.
• Start production adb logcat directly with shell disabled so the extension owns the process it terminates.
• Verify the adb executable, arguments, and shell option passed by AdbHelper.startLogCat.

Safety

Cleanup only uses extension-owned monitor and child-process handles. It does not terminate adb servers, emulators, VS Code, Node, PowerShell, or browsers globally by process name.

Validation

• npx prettier --check test\extension\android\androidPlatform.test.ts
• npm run build
• AdbHelper startLogCat parameter test passes in the Extension Host suite
• npm test: 307 tests executed, 1 skipped; one intermittent existing 2-second timeout occurred in packager.test.ts
• Relevant PID snapshot was unchanged before and after the run; no new adb logcat, repository Node, Extension Host, or Edge process remained

Closes #2855