[Windows] Skill shell execution opens interactive mintty (Git Bash) window that does not close

Description

On Windows, when a plugin skill executes inline shell commands, Claude Code invokes /usr/bin/bash --login -i <script-path> which opens a mintty (Git Bash) GUI terminal window. The window stays open and does not close automatically because of the -i (interactive) flag.

This happens on every command that triggers a skill with shell execution.

Environment

• OS: Windows 11 Pro 10.0.26200
• Shell: PowerShell (defaultShell: powershell)
• Plugin: pulse-dev-toolkit (covetrus-ai-marketplace)

Steps to Reproduce

1. Install a plugin that uses inline shell execution in its skills (e.g. pulse-dev-toolkit)
2. Trigger any skill that runs a shell command
3. A mintty window appears with the title: /usr/bin/bash --login -i C:\Users\<user>\.claude\plugins\cache\<marketplace-name>\...
4. The window remains open indefinitely

Expected Behavior

Skill shell commands should run silently/headlessly in the background without opening a visible terminal window. On Windows, bash should be invoked non-interactively (without -i) and with CREATE_NO_WINDOW so no mintty window appears.

Actual Behavior

/usr/bin/bash --login -i <script> is invoked, which causes mintty to open a visible interactive terminal window that does not auto-close.

Workaround

Setting disableSkillShellExecution: true in ~/.claude/settings.json prevents the popup but also disables all skill inline shell execution, degrading plugin functionality.

Additional Context

• defaultShell: powershell and CLAUDE_CODE_USE_POWERSHELL_TOOL=1 are already configured and do not affect this behaviour — the issue is in the skill runner, not the user-facing Bash tool.
• The fix should either remove the -i flag from the bash invocation, use PowerShell as the shell on Windows when defaultShell is set to powershell, or spawn the process with CREATE_NO_WINDOW.