feat: add Codex CLI plugin manifest (#350)

Add Codex plugin support for discovery via codex-plugin-scanner:
- .codex-plugin/plugin.json — plugin manifest
- .mcp.json — MCP server config (starts server_fastmcp)
- skills/skill-seekers/SKILL.md — bundled skill for Codex
- .gitignore — allow root .mcp.json to be tracked

Co-authored-by: internet-dot <28622406+internet-dot@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

skills/skill-seekers/SKILL.md

@@ -0,0 +1,69 @@
+---
+name: skill-builder
+description: Automatically detect source types and build AI skills using Skill Seekers. Use when the user wants to create skills from documentation, repos, PDFs, videos, or other knowledge sources.
+---
+
+# Skill Builder
+
+You have access to the Skill Seekers MCP server which provides 35 tools for converting knowledge sources into AI-ready skills.
+
+## When to Use This Skill
+
+Use this skill when the user:
+- Wants to create an AI skill from a documentation site, GitHub repo, PDF, video, or other source
+- Needs to convert documentation into a format suitable for LLM consumption
+- Wants to update or sync existing skills with their source documentation
+- Needs to export skills to vector databases (Weaviate, Chroma, FAISS, Qdrant)
+- Asks about scraping, converting, or packaging documentation for AI
+
+## Source Type Detection
+
+Automatically detect the source type from user input:
+
+| Input Pattern | Source Type | Tool to Use |
+|---------------|-------------|-------------|
+| `https://...` (not GitHub/YouTube) | Documentation | `scrape_docs` |
+| `owner/repo` or `github.com/...` | GitHub | `scrape_github` |
+| `*.pdf` | PDF | `scrape_pdf` |
+| YouTube/Vimeo URL or video file | Video | `scrape_video` |
+| Local directory path | Codebase | `scrape_codebase` |
+| `*.ipynb`, `*.html`, `*.yaml` (OpenAPI), `*.adoc`, `*.pptx`, `*.rss`, `*.1`-`.8` | Various | `scrape_generic` |
+| JSON config file | Unified | Use config with `scrape_docs` |
+
+## Recommended Workflow
+
+1. **Detect source type** from the user's input
+2. **Generate or fetch config** using `generate_config` or `fetch_config` if needed
+3. **Estimate scope** with `estimate_pages` for documentation sites
+4. **Scrape the source** using the appropriate scraping tool
+5. **Enhance** with `enhance_skill` if the user wants AI-powered improvements
+6. **Package** with `package_skill` for the target platform
+7. **Export to vector DB** if requested using `export_to_*` tools
+
+## Available MCP Tools
+
+### Config Management
+- `generate_config` — Generate a scraping config from a URL
+- `list_configs` — List available preset configs
+- `validate_config` — Validate a config file
+
+### Scraping (use based on source type)
+- `scrape_docs` — Documentation sites
+- `scrape_github` — GitHub repositories
+- `scrape_pdf` — PDF files
+- `scrape_video` — Video transcripts
+- `scrape_codebase` — Local code analysis
+- `scrape_generic` — Jupyter, HTML, OpenAPI, AsciiDoc, PPTX, RSS, manpage, Confluence, Notion, chat
+
+### Post-processing
+- `enhance_skill` — AI-powered skill enhancement
+- `package_skill` — Package for target platform
+- `upload_skill` — Upload to platform API
+- `install_skill` — End-to-end install workflow
+
+### Advanced
+- `detect_patterns` — Design pattern detection in code
+- `extract_test_examples` — Extract usage examples from tests
+- `build_how_to_guides` — Generate how-to guides from tests
+- `split_config` — Split large configs into focused skills
+- `export_to_weaviate`, `export_to_chroma`, `export_to_faiss`, `export_to_qdrant` — Vector DB export