Plugin skills not loaded in Claude Code when installed via marketplace: Missing skills/ directory structure

## Problem

Skills from this repository installed **via the official Claude Code marketplace feature** are **not loaded** by Claude Code, resulting in progressive disclosure not working.

## Installation Method

**Installed using:** Official Claude Code marketplace functionality ()
**NOT:** Manual git clone

The marketplace correctly installs the plugin to:
`~/.claude/plugins/marketplaces/anthropic-agent-skills/`

And shows in settings:
```json
"enabledPlugins": {
"document-skills@anthropic-agent-skills": true,
"example-skills@anthropic-agent-skills": true
}
```

## Environment

- Claude Code Version: Latest (2025-10-27)
- OS: macOS Darwin 24.6.0
- Installation: Via `/plugin marketplace add anthropics/skills`

## Debug Evidence

From `~/.claude/debug/latest`:

```
[DEBUG] Loading plugin document-skills from source: "./"
[DEBUG] Loading plugin example-skills from source: "./"
[DEBUG] Loaded 2 skills total (managed: 0, user: 2, project: 0)
[DEBUG] Total plugin skills loaded: 0 ← ❌ Problem!
```

User skills (manually placed in `~/.claude/skills/`) work fine: **2 loaded**
Plugin skills: **0 loaded**

## Root Cause

According to the [Claude Code Plugin documentation](https://docs.claude.com/en/docs/claude-code/plugins), plugins must have this structure:

```
my-plugin/
├── .claude-plugin/
│ └── plugin.json
├── skills/ ← ⚠️ REQUIRED
│ ├── skill-1/
│ │ └── SKILL.md
│ └── skill-2/
│ └── SKILL.md
```

**However, this repository (when installed via marketplace) has:**

```
anthropic-agent-skills/
├── .claude-plugin/
│ └── marketplace.json
├── mcp-builder/ ← ❌ Directly in root!
│ └── SKILL.md
├── document-skills/
│ ├── xlsx/
│ │ └── SKILL.md
├── skill-creator/
│ └── SKILL.md
```

The `marketplace.json` references skills with paths like:
```json
"skills": [
"./mcp-builder",
"./skill-creator",
"./document-skills/xlsx"
]
```

But Claude Code expects them under a `skills/` subdirectory to be loaded.

## Impact

- ❌ **Progressive disclosure does not work** - Skills are not automatically loaded into Claude's context
- ❌ **All marketplace skills affected** - mcp-builder, skill-creator, document-skills (xlsx, docx, pptx, pdf), canvas-design, algorithmic-art, webapp-testing, artifacts-builder, slack-gif-creator, theme-factory, brand-guidelines
- ❌ **Manual workaround required** - Users must manually copy skills to `~/.claude/skills/`
- ❌ **Inconsistent with documentation** - Official Anthropic repository doesn't follow official plugin structure documentation

## Expected Behavior

When plugins are enabled via marketplace installation:
1. Skills should be automatically discovered
2. Progressive disclosure should work (Skills loaded automatically based on semantic relevance)
3. Debug log should show: `Total plugin skills loaded: 10+`

## Proposed Solutions

1. **Restructure repository** - Add a `skills/` directory and move all skills into it
2. **Update Claude Code** - Support marketplace-specific flat structure (if intentional)
3. **Update documentation** - Clarify that marketplace structure differs from standard plugin structure

## Workaround

Manually copy skills to user directory:
```bash
cp -r ~/.claude/plugins/marketplaces/anthropic-agent-skills/mcp-builder ~/.claude/skills/
cp -r ~/.claude/plugins/marketplaces/anthropic-agent-skills/skill-creator ~/.claude/skills/
cp -r ~/.claude/plugins/marketplaces/anthropic-agent-skills/document-skills ~/.claude/skills/
# etc.
```

After copying, Claude Code correctly loads them:
```
[DEBUG] Loaded 5 skills total (managed: 0, user: 5, project: 0)
```

---

**This is a critical issue** as it prevents the core functionality (progressive disclosure) of Skills from working for users who install via the official marketplace method.