fix: launch presets wait for shell prompt before sending command

Was sending the command after a blind 300ms delay with \n — too early
for PowerShell startup banner, and \n caused a blank line before the
command.

Fix: poll mcp_terminal_read every 200ms until a prompt is detected
($, #, %, >, PS>), then send the command with \r (carriage return,
not newline). Falls back to sending after 5s timeout.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/ai/CopilotPanel.vue

@@ -156,11 +156,30 @@ async function launchPreset(preset: LaunchPreset): Promise<void> {
   if (!shell) return;
   selectedShell.value = shell;
   await launch();
-  // After shell spawns, send the preset command
+  // Wait for the shell prompt before sending the command.
+  // Poll the scrollback for a prompt indicator (PS>, $, #, %, >)
   if (sessionId && connected.value) {
-    setTimeout(() => {
-      invoke("pty_write", { sessionId, data: preset.command + "\n" }).catch(() => {});
-    }, 300);
+    const maxWait = 5000;
+    const start = Date.now();
+    const poll = setInterval(async () => {
+      if (Date.now() - start > maxWait) {
+        clearInterval(poll);
+        // Send anyway after timeout
+        invoke("pty_write", { sessionId, data: preset.command + "\r" }).catch(() => {});
+        return;
+      }
+      try {
+        const lines = await invoke<string>("mcp_terminal_read", { sessionId, lines: 3 });
+        const lastLine = lines.split("\n").pop()?.trim() || "";
+        // Detect common shell prompts
+        if (lastLine.endsWith("$") || lastLine.endsWith("#") || lastLine.endsWith("%") || lastLine.endsWith(">") || lastLine.endsWith("PS>")) {
+          clearInterval(poll);
+          invoke("pty_write", { sessionId, data: preset.command + "\r" }).catch(() => {});
+        }
+      } catch {
+        // Scrollback not ready yet, keep polling
+      }
+    }, 200);
   }
 }