fix: Switch auto-spawn from discuss to refine agent, surface in UI

The auto-spawned agent on initiative creation was using discuss mode
(Q&A) when it should use refine mode (expand content). Now:

- Description seeds root page as tiptap content (split on double newlines)
- Spawns refine agent with the populated page in inputContext
- getActiveRefineAgent broadened to also surface discuss agents (for
  CLI-spawned discuss agents)
- RefineAgentPanel shows mode-appropriate label for discuss vs refine

apps/web/src/components/CreateInitiativeDialog.tsx

@@ -123,7 +123,7 @@ export function CreateInitiativeDialog({
             <Label htmlFor="initiative-description">
               Description{" "}
               <span className="text-muted-foreground font-normal">
-                (optional — spawns a discuss agent)
+                (optional — seeds root page and spawns refine agent)
               </span>
             </Label>
             <Textarea

apps/web/src/components/editor/RefineAgentPanel.tsx

@@ -66,11 +66,12 @@ export function RefineAgentPanel({ initiativeId }: RefineAgentPanelProps) {
 
   // Running
   if (state === "running") {
+    const runningLabel = agent?.mode === 'discuss' ? 'Architect is discussing...' : 'Architect is refining...';
     return (
       <div className="mb-3 flex items-center gap-2 rounded-lg border border-border bg-card px-3 py-2">
         <Loader2 className="h-3.5 w-3.5 animate-spin text-primary" />
         <span className="text-sm text-muted-foreground">
-          Architect is refining...
+          {runningLabel}
         </span>
       </div>
     );