extraKnownMarketplaces with source: "directory" fails to load plugins from subdirectory

Bug: Plugins enabled via extraKnownMarketplaces using source: "directory" are not discovered when Claude Code is launched from a subdirectory of the git repo. Local skills/commands placed directly in .claude/ work fine from any subdirectory.

Repro steps:

1. In a git repo at /repo-root/, create .claude/settings.local.json:

{
  "enabledPlugins": {
    "myplugin@my-marketplace": true
  },
  "extraKnownMarketplaces": {
    "my-marketplace": {
      "source": {
        "source": "directory",
        "path": "/absolute/path/to/marketplace"
      }
    }
  }
}

1. The marketplace at the given path has a valid .claude-plugin/marketplace.json and a plugin with commands/skills.
2. cd /repo-root/ && claude — plugin commands work.
3. cd /repo-root/subdir/ && claude — plugin commands are not recognized.

Expected: Plugins resolve from any subdirectory within the repo, same as local .claude/skills/.

Actual: Plugin discovery silently fails from subdirectories. No error message shown.

Workaround: Enable plugins in user-scope settings (~/.claude/settings.local.json) instead of project-level.

Version: 2.1.101