feat: add optional you.com search plugin (keyless MCP server + you-web skill)

[mouse-value-add]

What this adds

A new you-com plugin that gives Claude Code sessions current web search through the You.com MCP server — search the web, read URLs, get cited answers. It fits next to insane-search (which solves access to blocked pages) by covering the discovery side: finding current sources in the first place.

Why through the marketplace

insane-search covers page access without keys, and insane-research builds reports, but neither is a search engine — there's no plugin in the Research & web category that takes a query and returns ranked, current web results. This adds that as an in-tree plugin using the existing mcpServers mechanism in the plugin manifest, which I understood is allowed for new plugins per CLAUDE.md ("신규는 in-tree 임시 허용").

What changed

• plugins/you-com/.claude-plugin/plugin.json — registers https://api.you.com/mcp?profile=free (keyless HTTP MCP server). This profile exposes the you-search tool with no API key and no signup.
• plugins/you-com/skills/you-web/SKILL.md — routes web-search / URL-reading / cited-synthesis requests to the available you-* tools, with a selection order and a graceful fallback when only the keyless you-search is available (gather sources by search, read pages with the host's web-fetch tool).
• plugins/you-com/README.md + LICENSE (MIT, matching the other plugins).
• .claude-plugin/marketplace.json — one entry (you-com, category productivity, same category as insane-search).
• README.md — badge 18 → 19, one row in the Research & web table.

Skill content is adapted from youdotcom-oss/agent-skills (MIT), which packages the same You.com skills for Claude Code, Codex, Copilot CLI and others (/plugin marketplace add youdotcom-oss/agent-skills).

Setup

• Default: zero setup. The keyless server URL is registered in the manifest — /plugin install you-com@gptaku-plugins is enough, and you-search works immediately.
• Optional upgrade: users who want full URL extraction (you-contents) and one-shot cited research (you-research) set YDC_API_KEY (free key from you.com/platform/api-keys) and point the server at https://api.you.com/mcp. Documented in the skill and README.

Usage

/plugin install you-com@gptaku-plugins

Use you-web to find the current stable Node.js version and cite sources.

Opt-in / failure behavior

• Nothing changes for existing users — the plugin adds files only; no default behavior, hooks, or dependencies are touched until a user installs and invokes it.
• No API key required for the default path; if the authenticated tools are absent, the skill degrades to you-search + host web-fetch instead of failing.

Validation

• python3 tools/validate_marketplace.py — passes for this change; the one remaining error (insane-crawl: unpublished development source must not be registered) is pre-existing on main (current CI run on main fails at the same step) and untouched by this PR.
• python3 tools/validate_commands.py — OK (24 command files scanned).
• python3 tools/validate_skill_contracts.py — OK (28 assertions).
• python3 tools/test_gptaku_doctor.py — 14 tests OK.
• Live check: initialize + tools/list against https://api.you.com/mcp?profile=free confirmed the keyless server responds and exposes you-search.
• tools/test_validate_marketplace.py requires Python ≥3.12 (typing.override); only 3.11 is available in my environment, but this PR doesn't touch that validator or its subject matter — it runs on 3.12 in CI.

Happy to adjust the shape if you'd prefer this as a submodule with its own repo instead of in-tree, or a different category — I followed the insane-crawl precedent for in-tree structure and kept the manifest minimal.