feat: add optional FastMCP skill for building MCP servers

Add FastMCP skill to optional-skills/mcp/fastmcp/ with:
- SKILL.md with workflow, design patterns, quality checklist
- Templates: API wrapper, database server, file processor
- Scaffold CLI script for template instantiation
- FastMCP CLI reference documentation

Moved to optional-skills (requires pip install fastmcp).

Based on work by kshitijk4poor in PR #2096.
Closes #343

optional-skills/mcp/fastmcp/templates/database_server.py

@@ -0,0 +1,77 @@
+from __future__ import annotations
+
+import os
+import re
+import sqlite3
+from typing import Any
+
+from fastmcp import FastMCP
+
+
+mcp = FastMCP("__SERVER_NAME__")
+
+DATABASE_PATH = os.getenv("SQLITE_PATH", "./app.db")
+MAX_ROWS = int(os.getenv("SQLITE_MAX_ROWS", "200"))
+TABLE_NAME_RE = re.compile(r"^[A-Za-z_][A-Za-z0-9_]*$")
+
+
+def _connect() -> sqlite3.Connection:
+    return sqlite3.connect(f"file:{DATABASE_PATH}?mode=ro", uri=True)
+
+
+def _reject_mutation(sql: str) -> None:
+    normalized = sql.strip().lower()
+    if not normalized.startswith("select"):
+        raise ValueError("Only SELECT queries are allowed")
+
+
+def _validate_table_name(table_name: str) -> str:
+    if not TABLE_NAME_RE.fullmatch(table_name):
+        raise ValueError("Invalid table name")
+    return table_name
+
+
+@mcp.tool
+def list_tables() -> list[str]:
+    """List user-defined SQLite tables."""
+    with _connect() as conn:
+        rows = conn.execute(
+            "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' ORDER BY name"
+        ).fetchall()
+    return [row[0] for row in rows]
+
+
+@mcp.tool
+def describe_table(table_name: str) -> list[dict[str, Any]]:
+    """Describe columns for a SQLite table."""
+    safe_table_name = _validate_table_name(table_name)
+    with _connect() as conn:
+        rows = conn.execute(f"PRAGMA table_info({safe_table_name})").fetchall()
+    return [
+        {
+            "cid": row[0],
+            "name": row[1],
+            "type": row[2],
+            "notnull": bool(row[3]),
+            "default": row[4],
+            "pk": bool(row[5]),
+        }
+        for row in rows
+    ]
+
+
+@mcp.tool
+def query(sql: str, limit: int = 50) -> dict[str, Any]:
+    """Run a read-only SELECT query and return rows plus column names."""
+    _reject_mutation(sql)
+    safe_limit = max(0, min(limit, MAX_ROWS))
+    wrapped_sql = f"SELECT * FROM ({sql.strip().rstrip(';')}) LIMIT {safe_limit}"
+    with _connect() as conn:
+        cursor = conn.execute(wrapped_sql)
+        columns = [column[0] for column in cursor.description or []]
+        rows = [dict(zip(columns, row)) for row in cursor.fetchall()]
+    return {"limit": safe_limit, "columns": columns, "rows": rows}
+
+
+if __name__ == "__main__":
+    mcp.run()