Add NetworkInspector lifecycle test coverage

[ConnorQi01]

Summary:

• Extend NetworkInspectorManager tests for full start-to-stop lifecycle.
• Assert non-macOS startup does not create/start the iOS tracker path.
• Preserve existing command early-return coverage for already-running Network Inspector.

Validation:

• npx tsc
• node .\node_modules\mocha\bin_mocha test\extension\networkInspector\networkInspectorManager.test.js test\extension\networkInspector\startStopCommands.test.js --ui tdd
• npm test (257 passing, 1 pending)

Fixes #2749