[Feature] Add unit tests for killPort command

Summary

The killPort command (src/extension/commands/killPort.ts) allows users to kill processes running on specific ports via the command palette, but currently lacks unit test coverage.

Motivation

• Test coverage gap: src/extension/commands/killPort.ts (40 lines) has no corresponding test file
• User-facing functionality: Command prompts user for port input and executes npx kill-port
• Error handling: Needs validation for invalid port inputs, command failures, and cancellation
• Process execution: Uses ChildProcess to run external command, needs mocking
• Pattern consistency: Most other command palette commands have test files

Current State

• Source file: src/extension/commands/killPort.ts
• No test file in test/extension/commands/
• Command extends ReactNativeCommand base class
• Uses VS Code showInputBox for user input
• Executes npx kill-port <port> via ChildProcess

Suggested Implementation

Add test/extension/commands/killPort.test.ts with coverage for:

• Valid port input and successful kill
• Invalid port input (non-numeric, empty)
• User cancellation (no input provided)
• ChildProcess execution failure
• Logger output verification

Follow existing test patterns from launchAndroidEmulator.test.ts and networkView.test.ts.

Validation

• Run npm test to ensure new tests pass
• Verify test coverage includes all code paths
• Check that mocks properly stub VS Code APIs and ChildProcess

Start with src/extension/commands/killPort.ts, then compare test patterns in launchAndroidEmulator.test.ts and networkView.test.ts. Add test/extension/commands/killPort.test.ts covering valid, invalid, cancelled, and failed ChildProcess cases, including logger output. Run npm test and confirm all code paths are covered.