herdr phase 2: Live Pane tab (xterm.js → node's herdr TUI)

The killer UX feature: click a mission's Live Pane tab and watch the
actual Herdr TUI on the target node in the browser — cursor, colors,
tool output, all live. WebRTC DataChannel direct where the browser
can reach the node peer-to-peer, WS-relayed fallback otherwise
(same auto-negotiation the INFRA node terminal already uses).

Zero new deployment infra — reuses the existing terminal_ticket +
terminal_ws + PTY-over-control-channel machinery. The one primitive
we grew: PtyTarget::Command variant so the node can spawn an
arbitrary program (\`herdr\`) in the PTY instead of the login shell.

Node daemon (clawmates-node):
  - PtyTarget grows a Command { argv } variant
  - spawn_command_pty resolves bare names against user + system bin
    dirs (matches how tool_update finds claude/kimi)
  - PtyTarget::from_frame reads the `command` array from the pty_open
    frame; precedence Command > Container > Host

cm-api:
  - NodeHub::open_pty grows an optional command argv; when set, the
    frame carries it and the daemon spawns the program directly.
  - routes::nodes::TermCtrl gains a `command: Vec<String>`; the
    fallback branch threads it through.

Frontend:
  - core.ts::webrtcConnector takes an optional commandOverride
    that ships inside the fallback frame
  - nodeHerdrConnector(nodeId) — mints the standard ticket + WS URL
    but overrides command to ["herdr"]
  - MissionCanvas grows a "pane" tab, visible only when
    runtime_kind='local_herdr'. LivePane subcomponent uses xterm.js
    (already a workspace dep) via useResilientTerminal, shows a
    connecting/relayed/direct pill in the corner.

To watch a mission live: pick "On a fleet node (Herdr)" + target
node in the wizard, launch, click Pane tab → node's Herdr TUI
appears. Navigate to the mission workspace in the Herdr sidebar
(mouse or prefix+w) to zoom into the mission's pane.

Focus-a-specific-pane-directly is a later enhancement — Herdr has
no CLI arg for it yet, so operator navigates the sidebar for now.

Verified: cargo check --workspace + tsc --noEmit both green.

frontend/src/components/dashboard/MissionCanvas.tsx

@@ -30,6 +30,12 @@ import {
 } from "@/lib/api/missions";
 import { MarkdownBlock } from "./MarkdownBlock";
 import { MissionWizard } from "./MissionWizard";
+import {
+  nodeHerdrConnector,
+  useResilientTerminal,
+  type TermMode,
+} from "@/components/computer/apps/terminal/core";
+import "@xterm/xterm/css/xterm.css";
 
 const mono =
   "ui-monospace, SFMono-Regular, SF Mono, Menlo, Monaco, Consolas, monospace";
@@ -70,7 +76,7 @@ const TEMPLATE_LABEL: Record<TemplateKind, string> = {
   custom: "Custom",
 };
 
-type Tab = "overview" | "phases" | "tasks" | "artifacts" | "benchmarks";
+type Tab = "overview" | "phases" | "tasks" | "artifacts" | "benchmarks" | "pane";
 
 export function MissionCanvas({
   selectedId,
@@ -438,7 +444,16 @@ export function MissionCanvas({
           />
         )}
         <div style={{ display: "flex", gap: 4, marginTop: 4 }}>
-          {(["overview", "phases", "tasks", "artifacts", "benchmarks"] as Tab[]).map((t) => {
+          {(
+            [
+              "overview",
+              "phases",
+              "tasks",
+              "artifacts",
+              "benchmarks",
+              ...(mission.runtime_kind === "local_herdr" ? (["pane"] as const) : []),
+            ] as Tab[]
+          ).map((t) => {
             const active = tab === t;
             const badge =
               t === "tasks"
@@ -918,6 +933,13 @@ export function MissionCanvas({
             )}
           </div>
         )}
+
+        {tab === "pane" && mission.runtime_kind === "local_herdr" && (
+          <LivePane
+            nodeId={mission.target_node_id}
+            visible={tab === "pane"}
+          />
+        )}
       </div>
     </div>
   );
@@ -970,6 +992,95 @@ function Empty({ label }: { label: string }) {
   );
 }
 
+function LivePane({
+  nodeId,
+  visible,
+}: {
+  nodeId: string | null;
+  visible: boolean;
+}) {
+  if (!nodeId) {
+    return (
+      <div
+        style={{
+          padding: 40,
+          textAlign: "center",
+          color: "#8a8a92",
+          fontSize: 13,
+        }}
+      >
+        This mission has no target node.
+      </div>
+    );
+  }
+  return <LivePaneInner nodeId={nodeId} visible={visible} />;
+}
+
+function LivePaneInner({
+  nodeId,
+  visible,
+}: {
+  nodeId: string;
+  visible: boolean;
+}) {
+  const [mode, setMode] = useState<TermMode>("connecting");
+  const { hostRef, refit } = useResilientTerminal(
+    {
+      connect: nodeHerdrConnector(nodeId, setMode),
+      autoFocus: false,
+      visible: () => visible,
+    },
+    [nodeId],
+  );
+  useEffect(() => {
+    if (visible) refit();
+  }, [visible, refit]);
+  return (
+    <div
+      style={{
+        position: "relative",
+        height: "70vh",
+        minHeight: 480,
+        background: "#0a0a0d",
+        borderRadius: 10,
+        border: "1px solid rgba(255,255,255,.06)",
+        overflow: "hidden",
+      }}
+    >
+      <div
+        style={{
+          position: "absolute",
+          top: 8,
+          right: 8,
+          zIndex: 5,
+          padding: "2px 8px",
+          borderRadius: 6,
+          fontFamily: mono,
+          fontSize: 10,
+          letterSpacing: ".1em",
+          textTransform: "uppercase",
+          color:
+            mode === "direct"
+              ? "#5fd08a"
+              : mode === "relayed"
+                ? "#8a8a92"
+                : "#e8b465",
+          background:
+            mode === "direct"
+              ? "rgba(95,208,138,.12)"
+              : "rgba(255,255,255,.05)",
+          border: `1px solid ${
+            mode === "direct" ? "rgba(95,208,138,.3)" : "rgba(255,255,255,.1)"
+          }`,
+        }}
+      >
+        {mode === "direct" ? "direct" : mode === "relayed" ? "relayed" : "connecting…"}
+      </div>
+      <div ref={hostRef} style={{ position: "absolute", inset: 0, padding: 8 }} />
+    </div>
+  );
+}
+
 function EditMissionModal({
   mission,
   onClose,