Plugin install fails on Windows: EPERM on case-insensitive rename

Description

/plugin installation fails on Windows with EPERM when the plugin cache rename collides with case-insensitive filesystem behavior.

Error

Error: Failed to install: EPERM: operation not permitted, rename 
'C:\Users\<user>\.claude\plugins\cache\ReVa' -> 
'C:\Users\<user>\.claude\plugins\cache\reva\ReVa\0.1.0'

Root Cause

Windows NTFS is case-insensitive by default. The rename tries to move ReVa into reva\ReVa\0.1.0, but ReVa and reva resolve to the same directory — so it's attempting to move a directory into a subdirectory of itself.

Repro

1. Windows 11 Pro (10.0.26100)
2. Run /plugin and install the ReVa plugin (MCP server from Ghidra reverse engineering tool)
3. Fails with EPERM

Deleting ~/.claude/plugins/cache/ReVa first does not fix the issue — the same conflict recurs on retry.

Expected

Plugin installation should handle case-insensitive filesystems correctly, e.g. by using a consistent case for the cache path or using a temp directory for the intermediate rename.

Environment

• Windows 11 Pro 10.0.26100
• Claude Code (latest as of 2026-02-19)