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/useSidebar.ts

@@ -189,6 +189,12 @@ function applyEvent(prev: SidebarResponse, event: import('./sessionEvents').Sess
     case 'git_diff_refresh':
       // Consumed by useGitDiff; no sidebar state change needed.
       return prev;
+    case 'open_orchestrator_pane':
+    case 'open_flow_launcher':
+    case 'flow_run_started':
+    case 'flow_run_step_updated':
+      // Consumed by useWorkspacePanes / OrchestratorPane / FlowLauncherDialog; sidebar has no stake.
+      return prev;
     case 'project_archived': {
       const next = prev.projects.filter((p) => p.id !== event.project_id);
       if (next.length === prev.projects.length) return prev;