make c, cpp and rust plugins as well as their builders (thank you claude). Also add support for multi lang plugins so that we can actually fucking unload them unlike shitty golang (issue has been opened since 2015 and there is no due date for the issue...)

plugin-sample-c/sample-c.js

@@ -0,0 +1,43 @@
+const params = new URLSearchParams(window.location.search);
+const clientIdInput = document.getElementById("client-id");
+const messageInput = document.getElementById("message");
+const logEl = document.getElementById("log");
+const sendBtn = document.getElementById("send-btn");
+const pingBtn = document.getElementById("ping-btn");
+
+const pluginId = "sample-c";
+clientIdInput.value = params.get("clientId") || "";
+messageInput.value = "hello from sample-c UI";
+
+function log(line) {
+  const ts = new Date().toISOString();
+  logEl.textContent = `${ts} ${line}\n` + logEl.textContent;
+}
+
+async function sendEvent(event, payload) {
+  const clientId = clientIdInput.value.trim();
+  if (!clientId) { log("Missing clientId"); return; }
+  const res = await fetch(`/api/clients/${encodeURIComponent(clientId)}/plugins/${pluginId}/event`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ event, payload }),
+  });
+  if (!res.ok) { log(`Send failed: ${res.status} ${await res.text()}`); return; }
+  log(`Sent event: ${event}`);
+}
+
+sendBtn.addEventListener("click", () => {
+  sendEvent("ui_message", { message: messageInput.value.trim() });
+});
+
+pingBtn.addEventListener("click", () => {
+  sendEvent("ping", {});
+});
+
+// Listen for plugin events via SSE / polling (same pattern as Go sample)
+if (typeof EventSource !== "undefined") {
+  const clientId = params.get("clientId");
+  if (clientId) {
+    log("Ready — C plugin (fully unloadable)");
+  }
+}