[BUG] EnabledPlugins in project settings causes schema validation crash when plugins not installed

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When .claude/settings.json contains enabledPlugins but the referenced plugins are not installed (e.g., in CI environments), Claude Code crashes with a cryptic Ajv JSON schema validation error instead of gracefully skipping or providing a clear error message.

What Should Happen?

Expected Behavior:

Skip missing plugins with a warning, OR
Fail with clear error: "Plugin 'context7@claude-plugins-official' not found. Install it or remove from enabledPlugins."

Error Messages/Logs

Crashes after 410ms with minified Ajv schema validation error:
SDK execution error: 14 |     depsCount: ${Q},
15 |     deps: ${$}}`};var Mj={keyword:"dependencies",type:"object",schemaType:"object"...
error: Claude Code process exited with code 1
Impact:

Steps to Reproduce

Create .claude/settings.json with:

{
  "enabledPlugins": {
    "context7@claude-plugins-official": true
  }
}

Run Claude Code in an environment where plugins are NOT installed (fresh CI runner, new machine)
Claude Code crashes immediately

Forces choice between: (a) no project plugins, or (b) installing plugins in every CI step
Schema validation happens before plugin loading, making it impossible to gracefully degrade

Environment:

Claude Code version: 2.1.19
claude-code-action@v1
GitHub Actions runner (ubuntu-latest)

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.19

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_