DEP0190: shell spawn on Windows breaks multi-word prompts in watch capabilities #1389

Bug

Running squad watch --execute --copilot-flags "--yolo" --monitor-email on Windows produces:

1. Node DEP0190 deprecation warning about shell: true with args being a security risk
2. The system cannot find the file specified error from monitor-email (and other legacy capabilities)

Steps to Reproduce

1. Have copilot CLI installed (works fine standalone)
2. Run: npx @bradygaster/squad-cli@insider watch --execute --copilot-flags "--yolo" --monitor-email
3. Observe the error during the first check round

Root Cause

execFile(cmd, args, { shell: true }) on Windows does NOT quote args before concatenating them. The multi-word prompt string gets split by cmd.exe into fragments that it interprets as file paths.

Environment

• Windows 11
• Node v20+
• squad-cli@insider (v0.10.0-insider.1)
• copilot CLI installed via both WinGet (.exe) and npm (.cmd wrapper)

Fix

PR #1388