feat: in-app Orchestrator (Phase 2) — multi-agent conductor

Brings the deterministic Han-flow conductor into BooCode: launch any read-only
flow from BooChat or BooCoder, watch each agent stream live in a Paseo-style
run pane, get an evidence-disciplined report — on local Qwen, persisted and
resumable. Read-only enforced hard via qwen --approval-mode plan (orchestrator
tasks fail closed if qwen is unavailable; never fall to write-capable native).

Backend (apps/coder): re-homed conductor defs, flow_runs/flow_steps schema,
flow-runner + dispatcher onTaskTerminal hook, restart-resume, runs routes
(launch/list/get/cancel), user-channel WS. Contracts: two flow_run_* frames.
Web: orchestrator pane kind + OrchestratorPane, Workflow button + slash flows
(BooChat/BooCoder parity), FlowLauncherDialog, "New Orchestrator" in the + and
split menus, runs history + export. Plan: openspec/changes/orchestrator.

apps/web/src/hooks/useWorkspacePanes.ts

@@ -6,6 +6,7 @@ import type {
   ClosedPaneEntry,
   HtmlArtifactState,
   MarkdownArtifactState,
+  OrchestratorState,
   WorkspacePane,
   WorkspaceState,
   WorkspaceTabKind,
@@ -176,6 +177,16 @@ function htmlArtifactPane(state: HtmlArtifactState): WorkspacePane {
   };
 }
 
+function orchestratorPane(state: OrchestratorState): WorkspacePane {
+  return {
+    id: generateId(),
+    kind: 'orchestrator',
+    chatIds: [],
+    activeChatIdx: -1,
+    orchestrator_state: state,
+  };
+}
+
 // v1.9: settings panes are ephemeral. Filter them out before persisting so a
 // page reload always returns to a clean workspace; the user re-opens via the
 // sidebar Settings button when needed.
@@ -277,6 +288,8 @@ export interface UseWorkspacePanesResult {
   addSplitPane: (kind: 'chat' | 'terminal' | 'coder') => string | null;
   /** Mixed tabs: add a tab of any kind to a pane (the "+" menu). */
   createTab: (paneIdx: number, kind: WorkspaceTabKind) => Promise<void>;
+  /** Open an orchestrator run pane (or focus an existing one for the same run_id). */
+  addOrchestratorPane: (state: OrchestratorState) => string | null;
   /** Back-compat alias for createTab(paneIdx, 'coder'). */
   createCoderTab: (paneIdx: number) => Promise<void>;
   // Open-on-first-click, close-on-second-click. Singleton — settings panes
@@ -831,6 +844,39 @@ export function useWorkspacePanes(sessionId: string): UseWorkspacePanesResult {
     return success ? newPaneId : null;
   }, [seedPaneChat]);
 
+  const addOrchestratorPane = useCallback((state: OrchestratorState): string | null => {
+    let openedId: string | null = null;
+    setPanes((prev) => {
+      // Dedup: focus an existing pane for the same run.
+      const existingIdx = prev.findIndex(
+        (p) => p.kind === 'orchestrator' && p.orchestrator_state?.run_id === state.run_id,
+      );
+      if (existingIdx >= 0) {
+        setActivePaneIdx(existingIdx);
+        openedId = prev[existingIdx]!.id;
+        return prev;
+      }
+      if (nonSettingsCount(prev) >= MAX_PANES) {
+        toast.error(`Maximum ${MAX_PANES} panes`);
+        return prev;
+      }
+      const newPane = orchestratorPane(state);
+      openedId = newPane.id;
+      const next = [...prev, newPane];
+      setActivePaneIdx(next.length - 1);
+      return next;
+    });
+    return openedId;
+  }, []);
+
+  // Orchestrator pane: open via sessionEvents (fired by ChatInput slash/button).
+  useEffect(() => {
+    return sessionEvents.subscribe((ev) => {
+      if (ev.type !== 'open_orchestrator_pane') return;
+      addOrchestratorPane(ev.state);
+    });
+  }, [addOrchestratorPane]);
+
   // Returns the new settings pane id when one is OPENED (so mobile callers can
   // push ?pane= atomically — see addPaneAndSwitch), or null when it was closed.
   // Id generated outside the updater so a strict-mode double-invoke agrees.
@@ -1074,6 +1120,7 @@ export function useWorkspacePanes(sessionId: string): UseWorkspacePanesResult {
     closeSessionHistory,
     addSplitPane,
     createTab,
+    addOrchestratorPane,
     createCoderTab,
     toggleSettingsPane,
     removePane,