Agent worktree isolation fails on Windows due to case-insensitive path mismatch

Bug Description

isolation: "worktree" in the Agent tool fails on Windows with:

Cannot create agent worktree: not in a git repository and no WorktreeCreate hooks are configured.

The repository is valid — git status, git worktree list, and git push all work correctly.

Root Cause

Case mismatch between shell working directory and git's reported toplevel:

$ pwd
/x/dev/growgeneration

$ git rev-parse --show-toplevel
X:/Dev/GrowGeneration

The Agent tool's git repository detection appears to do a case-sensitive path check, which fails on Windows (case-insensitive filesystem).

Environment

• OS: Windows 11 Home 10.0.26200
• Shell: Git Bash (MSYS2)
• Drive: X:\ (mapped/external drive)
• Claude Code version: Latest (auto-updates enabled)
• Model: claude-opus-4-6

Steps to Reproduce

1. Open Claude Code on Windows in a git repository on a non-C: drive
2. Use the Agent tool with isolation: "worktree"
3. Observe the error despite being in a valid git repo

Expected Behavior

Git repository detection should use case-insensitive path comparison on Windows, or normalize paths before comparing.

Workaround

Set workflow.use_worktrees to false and run agents sequentially.