[DOCS]: Agents field as string in plugin manifest causes installation failure

Summary

The public plugin docs show agents as a string value in the example manifest schema, but using a string causes plugin installation to fail. Only an array of strings works.

Problem

The Plugin Manifest Schema docs show the following example:

{
  "agents": "./custom/agents/"
}

However, using a string for the agents field causes plugin installation to silently fail. The plugin does not load correctly and no clear error is surfaced to the user.

The only format that works is an array of strings:

{
  "agents": ["./agents/broll-manager.md"]
}

The internal manifest reference (plugins/plugin-dev/skills/plugin-structure/references/manifest-reference.md) specifies agents as String or Array of strings with default ["./agents"], but the string variant does not appear to work in practice.

Steps to Reproduce

1. Create a plugin with plugin.json containing "agents": "./agents/"
2. Add the plugin to the marketplace and install it from the marketplace
3. Plugin installation fails -- agents are not loaded and no clear error is surfaced

1. Change to "agents": ["./agents/my-agent.md"]
2. Re-publish and reinstall from the marketplace
3. Agents now load correctly

Expected Behavior

Either:

• The string format ("agents": "./agents/") should work as documented, OR
• The docs should be updated to show only the array-of-strings format that actually works

Related Issues

• #13927 -- agents array of objects causes Zod validation error in TUI
• #20409 -- Silent skill loading failure with unknown/malformed fields
• affaan-m/everything-claude-code#90 -- Community report on manifest schema confusion
• affaan-m/everything-claude-code#93 -- Community report on skill loading issues