[BUG] Plugin installer uses incorrect (lowercased) home directory path when username contains uppercase letters or dots

Platform: macOS Darwin 25.5.0
Claude Code version: 2.1.71

Description:
When installing a plugin, Claude Code resolves the home directory incorrectly when the macOS username contains uppercase letters or dots (e.g., /Users/First.Last style usernames).

Error:

Failed to install: Source path does not exist:
/Users/<lowercased-username>/.claude/plugins/marketplaces/claude-plugins-official/plugins/<plugin-name>

The installer appears to lowercase and strip dots from the username instead of using the actual $HOME path.

Expected: Plugin installer should use the correct $HOME path.
Actual: Username is normalized to lowercase with dots removed, causing the resolved path to not exist.

Workaround:

sudo ln -s $HOME /Users/<normalized-username>