[FEATURE] Persistent in-place plugin loading (no cache)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When developing plugins with feedback loops that modify their own source code (e.g., self-improving plugins, learning systems), the current caching behavior breaks the workflow:

1. Plugins installed via claude plugin install are copied to cache (~/.claude/plugins/cache/)
2. Any edits made by the plugin go to the cached copy, not the original source
3. Changes are lost on reinstall/update

The --plugin-dir flag solves this by loading plugins in-place without caching, but it's session-only and must be specified every time.

Current Workarounds:

• Use --plugin-dir every session (tedious, requires alias/wrapper)
• Manually symlink cache directories to source (fragile, breaks on update)
• Store mutable state outside the plugin (requires restructuring)

Proposed Solution

Add a persistent way to load plugins in-place.

Option A: pluginDirs in settings.json

{
  "pluginDirs": [
    "/path/to/my-plugins"
  ]
}

Alternative Solutions

Option B: Per-plugin cache: false option

{
  "plugins": {
    "my-plugin@my-marketplace": {
      "cache": false
    }
  }
}

Option C: --plugin-dir equivalent in settings

{
  "defaultPluginDirs": [
    "/path/to/dev-plugins"
  ]
}

Priority

High - Significant impact on productivity

Feature Category

Plugin system

Use Case Example

• Self-improving plugins: Sessions edit plugin source for continuous improvement
• Plugin development: Rapid iteration without reinstalling
• Shared team plugins: Single source of truth on network drive
• Local marketplaces: Development workflows where source = runtime

Additional Context

The --plugin-dir flag already implements the desired behavior—this request is simply to make it persistent via configuration.