feat: add MCP server with HTML artifact tools

docs/MCP_STDIO.md

@@ -0,0 +1,26 @@
+# MCP stdio integration
+
+The MCP server lives in mcp/.
+
+Use it when ChatGPT or a Gateway should call html-explainer as a tool instead of relying only on remembered instructions.
+
+## First version
+
+The first version is intentionally conservative:
+
+- stdio transport
+- official MCP TypeScript SDK
+- read/list/audit/validate tools only
+- repo-root path safety
+- smoke test
+- no artifact generation yet
+
+## Why this is minimal
+
+The repo is now strong enough conceptually. The MCP risk is operational: bad schemas, unstable stdio, unsafe paths, or too much generation logic in the server.
+
+This version avoids those risks and proves the connection layer first.
+
+## Next step
+
+After stdio and Gateway are stable, add generation tools in a separate PR.

mcp/.gitignore

@@ -0,0 +1 @@
+node_modules/

mcp/README.md

@@ -0,0 +1,34 @@
+# html-explainer MCP
+
+Minimal stdio MCP server for html-explainer.
+
+## Scope
+
+This first version proves the connection layer. It exposes read, audit, and validation tools.
+
+It does not generate or write artifacts yet.
+
+## Tools
+
+- html_explainer_status
+- html_explainer_list_patterns
+- html_explainer_get_golden_cases
+- html_explainer_read_product_doc
+- html_explainer_audit_file
+- html_explainer_validate_repo
+
+## Run
+
+From the mcp folder:
+
+npm install
+npm test
+npm start
+
+## Gateway command
+
+node /absolute/path/to/html-explainer/mcp/src/server.js
+
+## Rollback
+
+Delete the mcp folder.