Windows: spawn EINVAL in watch capabilities (execFile without shell:true) #920

Bug: Windows spawn EINVAL in watch capabilities that use execFile()

Environment

• OS: Windows 11
• Node: v22+
• squad-cli: @bradygaster/squad-cli@0.9.4-insider.1
• agency: 2026.4.8.1

Problem

Capabilities monitor-teams, monitor-email, retro, and decision-hygiene fail with spawn EINVAL on Windows when running watch --execute.

Root Cause

These capabilities use execFile(cmd, args, ...) without shell: true. On Windows, execFile cannot:

1. Resolve bare command names (like gh) through PATH
2. Execute .cmd/.bat wrapper scripts

The execute capability works fine because it handles this differently.

Additional Issue

These capabilities hardcode gh copilot --message but don't respect the agentCmd config. Users with copilot.exe (standalone WinGet) or agency CLI can't use these capabilities even with a working agentCmd configured.

Suggested Fix

1. Add shell: true to the execFile options in spawnWithTimeout()
2. Have all capabilities respect agentCmd from config (not just execute)

Workaround

Disable the broken capabilities in .squad/config.json:

{
  "watch": {
    "monitor-teams": false,
    "monitor-email": false,
    "retro": false,
    "decision-hygiene": false
  }
}

Output

spawn EINVAL on monitor-teams, monitor-email, retro, decision-hygiene