Add prefab auto-wiring for MCP Apps (#3119)

Tools that return prefab types (UIResponse, Component) automatically get
wired to the shared prefab renderer resource. Works via app=True,
return type inference, or both.

examples/apps/datatable_server.py

@@ -0,0 +1,165 @@
+"""DataTable MCP App — interactive, sortable data views with Prefab.
+
+Demonstrates `fastmcp[apps]` with Prefab UI components:
+- `app=True` for automatic renderer wiring
+- `UIResponse` with `DataTable` for rich tabular output
+- Searchable, sortable, paginated tables
+- Layout composition with `Column`, `Heading`, `Text`, and `Badge`
+
+Usage:
+    uv run python datatable_server.py              # HTTP (port 8000)
+    uv run python datatable_server.py --stdio       # stdio for MCP clients
+"""
+
+from __future__ import annotations
+
+from prefab_ui import UIResponse
+from prefab_ui.components import (
+    Badge,
+    Column,
+    DataTable,
+    DataTableColumn,
+    Heading,
+    Muted,
+    Row,
+)
+
+from fastmcp import FastMCP
+
+mcp = FastMCP("Team Directory")
+
+EMPLOYEES = [
+    {
+        "name": "Alice Chen",
+        "role": "Engineering",
+        "level": "Senior",
+        "location": "San Francisco",
+        "status": "active",
+    },
+    {
+        "name": "Bob Martinez",
+        "role": "Design",
+        "level": "Lead",
+        "location": "New York",
+        "status": "active",
+    },
+    {
+        "name": "Carol Johnson",
+        "role": "Engineering",
+        "level": "Staff",
+        "location": "London",
+        "status": "active",
+    },
+    {
+        "name": "David Kim",
+        "role": "Product",
+        "level": "Senior",
+        "location": "San Francisco",
+        "status": "away",
+    },
+    {
+        "name": "Eva Müller",
+        "role": "Engineering",
+        "level": "Mid",
+        "location": "Berlin",
+        "status": "active",
+    },
+    {
+        "name": "Frank Okafor",
+        "role": "Data Science",
+        "level": "Senior",
+        "location": "Lagos",
+        "status": "active",
+    },
+    {
+        "name": "Grace Liu",
+        "role": "Engineering",
+        "level": "Junior",
+        "location": "Singapore",
+        "status": "active",
+    },
+    {
+        "name": "Hassan Ali",
+        "role": "Design",
+        "level": "Senior",
+        "location": "Dubai",
+        "status": "away",
+    },
+    {
+        "name": "Iris Tanaka",
+        "role": "Product",
+        "level": "Lead",
+        "location": "Tokyo",
+        "status": "active",
+    },
+    {
+        "name": "James Wright",
+        "role": "Engineering",
+        "level": "Senior",
+        "location": "London",
+        "status": "inactive",
+    },
+    {
+        "name": "Karen Petrov",
+        "role": "Data Science",
+        "level": "Lead",
+        "location": "Berlin",
+        "status": "active",
+    },
+    {
+        "name": "Liam O'Brien",
+        "role": "Engineering",
+        "level": "Mid",
+        "location": "Dublin",
+        "status": "active",
+    },
+]
+
+
+@mcp.tool(app=True)
+def list_team(department: str | None = None) -> UIResponse:
+    """Browse the team directory with sorting and search.
+
+    Args:
+        department: Filter by department (e.g. "Engineering", "Design").
+                    Leave empty to show everyone.
+    """
+    if department:
+        rows = [e for e in EMPLOYEES if e["role"].lower() == department.lower()]
+    else:
+        rows = EMPLOYEES
+
+    active = sum(1 for e in rows if e["status"] == "active")
+
+    with Column(gap=6, css_class="p-6") as view:
+        with Column(gap=1):
+            Heading("Team Directory")
+            with Row(gap=2):
+                Muted(f"{len(rows)} members")
+                Muted(f"{active} active", css_class="text-success")
+                if department:
+                    Badge(department, variant="outline")
+
+        DataTable(
+            columns=[
+                DataTableColumn(key="name", header="Name", sortable=True),
+                DataTableColumn(key="role", header="Department", sortable=True),
+                DataTableColumn(key="level", header="Level", sortable=True),
+                DataTableColumn(key="location", header="Location", sortable=True),
+                DataTableColumn(key="status", header="Status", sortable=True),
+            ],
+            rows=rows,
+            searchable=True,
+            paginated=True,
+            page_size=10,
+        )
+
+    return UIResponse(
+        view=view,
+        state={"total": len(rows), "active": active},
+        text=f"Team directory: {len(rows)} members ({active} active)",
+    )
+
+
+if __name__ == "__main__":
+    mcp.run()