Plugin/skill discovery doesn't traverse parent directories

Description

When Claude Code is launched from a subdirectory of a git repo, plugins enabled in the repo root's .claude/settings.json are not discovered. The plugin loader appears to only check the CWD for .claude/settings.json, unlike CLAUDE.md which correctly traverses up the directory tree.

Repro

Given this repo structure:

repo-root/
├── .claude/
│   └── settings.json          ← has enabledPlugins + extraKnownMarketplaces
└── deeply/nested/subdir/
    └── (no .claude/settings.json)

1. Launch Claude Code from repo-root/ → /skills shows all plugin skills ✅
2. Launch Claude Code from repo-root/deeply/nested/subdir/ → /skills shows 0 plugin skills ❌
3. /reload-plugins from the subdirectory reports 0 plugins · 0 skills

Expected behavior

Plugins enabled in a parent directory's .claude/settings.json (up to the git root) should be inherited by subdirectories, consistent with how CLAUDE.md files are resolved.

Environment

• Claude Code v2.1.92
• macOS (Darwin 25.4.0)
• Custom marketplace plugin (extraKnownMarketplaces pointing to a private GitHub repo)
• installed_plugins.json has the plugin scoped to the repo root projectPath

Workaround

Duplicate the .claude/settings.json (with enabledPlugins and extraKnownMarketplaces) into the subdirectory.