feat(electrobun): wire PTY daemon into terminal tabs via Electrobun RPC

- Bun process connects to agor-ptyd via PtyClient (5 retries, exponential backoff)
- RPC bridge: 5 request handlers (create/write/resize/unsubscribe/close)
- Daemon output forwarded to WebView as pty.output messages (base64 passthrough)
- Terminal.svelte: real PTY sessions via RPC instead of echo mode
- Shared RPC schema at src/shared/pty-rpc-schema.ts
- Fixed pty-client.ts protocol: base64 string for data (was number array)
- TerminalTabs passes sessionId to Terminal component

ui-electrobun/src/mainview/main.ts

@@ -2,9 +2,39 @@ import "./app.css";
 import "@xterm/xterm/css/xterm.css";
 import App from "./App.svelte";
 import { mount } from "svelte";
+import { Electroview } from "electrobun/view";
+import type { PtyRPCSchema } from "../shared/pty-rpc-schema.ts";
+
+/**
+ * Set up Electroview RPC.
+ *
+ * The schema is split from the Bun side's perspective:
+ *   - "requests"  in PtyRPCSchema = what WE (WebView) call on Bun → these become
+ *                 methods on electrobun.rpc.request.*
+ *   - "messages"  in PtyRPCSchema = what BUN pushes to us → we listen via
+ *                 electrobun.rpc.addMessageListener(name, handler)
+ *
+ * Electroview.defineRPC takes the schema where handlers.requests = what the
+ * WebView handles (i.e., requests FROM Bun to us). Since Bun never calls us
+ * with requests (only messages), that section is empty.
+ */
+const rpc = Electroview.defineRPC<PtyRPCSchema>({
+  maxRequestTime: 10_000,
+  handlers: {
+    requests: {
+      // No request handlers needed — Bun only pushes messages to us, not requests.
+    },
+    messages: {
+      // These are messages that WE send to Bun (fire-and-forget).
+      // Empty: WebView doesn't initiate any fire-and-forget messages.
+    },
+  },
+});
+
+export const electrobun = new Electroview({ rpc });
 
 const app = mount(App, {
-	target: document.getElementById("app")!,
+  target: document.getElementById("app")!,
 });
 
 export default app;