Add example: Bun HTTP server showcasing jrx JSX-to-JSON rendering

Bun React app with HMR that demonstrates jrx's render() pipeline.
Shows JSX source, live UI via @json-render/react, and JSON output
side by side.

- example/specs/simple.tsx: flat Stack > Text + Button
- example/specs/full.tsx: nested layout with state, events,
  visibility conditions, and watchers
- Uses defineCatalog + defineRegistry from @json-render/react
- Fix package.json exports to match actual tsup output (.js/.cjs
  instead of .mjs/.js)

Co-authored-by: Ona <no-reply@ona.com>

example/specs/full.tsx

@@ -0,0 +1,75 @@
+/** @jsxImportSource jrx */
+import { render } from "jrx";
+import { Stack, Card, Text, Button, Input } from "../components";
+
+export const fullSpec = render(
+  <Stack>
+    <Card title="Counter">
+      <Text content={{ $state: "/count" }} />
+      <Button
+        label="Increment"
+        on={{
+          press: {
+            action: "increment",
+            params: { statePath: "/count" },
+          },
+        }}
+      />
+    </Card>
+
+    <Card title="Toggle Details">
+      <Button
+        label={{
+          $cond: { $state: "/showDetails", eq: true },
+          $then: "Hide Details",
+          $else: "Show Details",
+        }}
+        on={{
+          press: {
+            action: "setState",
+            params: {
+              statePath: "/showDetails",
+              value: {
+                $cond: { $state: "/showDetails", eq: true },
+                $then: false,
+                $else: true,
+              },
+            },
+          },
+        }}
+      />
+      <Text
+        content="These are the hidden details!"
+        visible={{ $state: "/showDetails", eq: true }}
+      />
+    </Card>
+
+    <Card title="Watched Input">
+      <Input
+        placeholder="Type a country..."
+        on={{
+          change: {
+            action: "setState",
+            params: { statePath: "/country", value: { $event: "/value" } },
+          },
+        }}
+      />
+      <Text
+        content={{ $state: "/country" }}
+        watch={{
+          "/country": {
+            action: "logCountry",
+            params: { country: { $state: "/country" } },
+          },
+        }}
+      />
+    </Card>
+  </Stack>,
+  {
+    state: {
+      count: 0,
+      showDetails: false,
+      country: "",
+    },
+  }
+);