[Feature] Fix StopLogCatMonitor QuickPick cancellation and add unit tests

[ConnorQi01]

Summary

stopLogCatMonitor hangs indefinitely when the user cancels the device-selection QuickPick. The code uses await new Promise(() => {}) as a placeholder (marked #todo!>selectionHandling>), which leaves the command permanently pending instead of exiting cleanly. No unit tests exist for this command.

Why this is useful

Users who accidentally open the Stop LogCat Monitor command and press Escape are silently blocked — the command never completes and no error is shown. Fixing this makes the command behave consistently with other command-palette flows that handle QuickPick cancellation with a clean early return.

Suggested scope

• Replace await new Promise(() => {}) with an early return (or an explicit cancellation notice) in selectLogCatMonitor at src/extension/commands/stopLogCatMonitor.ts:39
• Add unit tests covering:
  • No monitors running → AndroidCouldNotFindActiveLogCatMonitor error thrown
  • Exactly one monitor running → monitor deleted without showing QuickPick
  • Multiple monitors running, user selects one → selected monitor deleted
  • Multiple monitors running, user cancels QuickPick → command exits cleanly, no monitor deleted

Evidence

• src/extension/commands/stopLogCatMonitor.ts lines 37–42: #todo!>selectionHandling> comment with await new Promise(() => {}) as the cancel path
• No test file exists under test/extension/commands/ for stopLogCatMonitor
• Similar cancellation coverage was already tracked for SetNewArch in issue [Feature] add coverage for Set New Architecture flow when second QuickPick is cancelled #2751

Validation

• Run the new unit tests: npm test (mocha suite for stopLogCatMonitor)
• Manually open "Stop React Native LogCat Monitor" with multiple active monitors and press Escape — command should exit without hanging