P2: MSYS path resolution fails on Windows git-bash — double drive letter

[ar27111994]

Summary

Using /c/Projects/... MSYS paths on Windows git-bash produces Error: Cannot find module 'C:\c\Projects\...' (doubled drive letter). Users must use native Windows paths with proper quoting.

Verification

Tested on main HEAD c3e58e9 (v2.0.0). Shell: MSYS/git-bash on Windows 10.

# BROKEN — MSYS path
$ node /c/Projects/agent-harness/dist/cli.js --version
Error: Cannot find module 'C:\c\Projects\agent-harness\dist\cli.js'

# WORKS — native Windows path
$ node "C:\Projects\agent-harness\dist\cli.js" --version
2.0.0

Root Cause

MSYS/bash auto-converts /c/... to C:/... but Node's module resolver sometimes re-applies the drive letter prefix, producing C:\c\....

Impact

• README examples using /c/... paths won't work on the most common Windows shell
• First-run experience broken for Windows git-bash users
• README quick start "from source" instructions unreliable

Acceptance Criteria

• README quick start includes Windows git-bash path note
• At least one invocation method works reliably from git-bash
• Troubleshooting guide covers this failure mode

Priority / Effort

Priority: P2 Effort: S