Add doc on creating Wifi Antenna

docs/guides/tscircuit-essentials/draw-a-wifi-antenna.mdx

@@ -0,0 +1,52 @@
+---
+title: Draw a WiFi Antenna
+description: >-
+  Draw an open-ended PCB antenna shape from a chip pin with a manual trace path.
+---
+
+import CircuitPreview from "@site/src/components/CircuitPreview"
+
+# Draw a WiFi Antenna
+
+Use a manual trace path when you want to draw open-ended copper from an RF pin,
+such as a simple WiFi antenna or antenna feed. Instead of using `from` and `to`,
+provide a `path` with the RF pin selector and define the copper shape with
+`pcbPath`.
+
+<CircuitPreview leftView="code" rightView="pcb" code={`
+  export default () => (
+    <board width="32mm" height="16mm">
+      <chip name="U1" footprint="qfn32" />
+      <trace
+        path={[".U1 > .pin1"]}
+        width="0.3mm"
+        pcbPath={[
+          ".U1 > .pin1",
+          { x: -2.5, y: 4.2 },
+          { x: 4.0, y: 4.2 },
+          { x: 4.0, y: 6.6 },
+          { x: 15.0, y: 6.6 },
+          { x: 15.0, y: 5.2 },
+          { x: 6.0, y: 5.2 },
+          { x: 6.0, y: 3.8 },
+          { x: 15.0, y: 3.8 },
+          { x: 15.0, y: 2.4 },
+          { x: 6.0, y: 2.4 },
+          { x: 6.0, y: 1.0 },
+          { x: 15.0, y: 1.0 },
+        ]}
+      />
+    </board>
+  )
+`} />
+
+The `pcbPath` points are PCB coordinates in millimeters. This example draws a
+meandered printed antenna near the board edge. Adjust the points to change the
+overall length, spacing between runs, and feed location.
+
+:::caution
+This controls the antenna geometry in tscircuit, but it does not calculate RF
+performance. For a production WiFi antenna, tune the dimensions, trace width,
+clearance, stackup, and ground keepout for your target frequency and PCB
+manufacturer.
+:::