stop showing opencode placeholder titles as if they were names

OpenCode titles a session from the conversation, but asynchronously — a finished turn of
ours ended up called "Single color in oc-red2.png", better than anything we would generate.
Until then the session is literally named "New session - 2026-08-10T15:44:17.178Z".

That window is exactly when a session is most visible: /chat/live shows turns that are
RUNNING, so the placeholder is what the panel catches, and a live row was being labelled
with a timestamp string.

Recognise it and treat it as untitled, so the good name arrives on its own. Passing --title
on the run was the other option and is worse: it fixes the transient case by permanently
replacing opencode own title with a truncated prompt, degrading it where it lasts longest.

A pattern match rather than startsWith, because a genuine title is allowed to begin with
those words. Two defects the tests caught while writing them: a whitespace-only title was
not treated as unnamed, and the mapping let undefined through where a string was required.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/api/chat/opencode-sessions.ts

@@ -24,6 +24,23 @@ import { logger } from './logger';
  * the `!cwd` escape never fired either and there was no configuration in which an OpenCode session
  * appeared in /chat. Verified against the live server: 7 sessions present, 0 returned.
  */
+/**
+ * OpenCode's own placeholder name for a session it has not titled yet.
+ *
+ * It titles a session from the conversation, but ASYNCHRONOUSLY and after there is something to read —
+ * a finished turn ends up called "Single color in oc-red2.png", which is better than anything we would
+ * generate. Until then the session is literally named `New session - 2026-08-10T15:44:17.178Z`.
+ *
+ * That window is exactly when a session is most visible: `/chat/live` shows turns that are RUNNING, so
+ * the placeholder is what the panel catches. Treating it as "not yet titled" lets the good name arrive
+ * on its own. Forcing `--title` on the run instead would fix the transient case by permanently
+ * replacing opencode's title with a truncated prompt — worse where it lasts longest.
+ */
+export const isPlaceholderOpenCodeTitle = (title: string | undefined): boolean => {
+  const trimmed = title?.trim();
+  return !trimmed || /^New session - \d{4}-\d{2}-\d{2}T[\d:.]+Z?$/.test(trimmed);
+};
+
 export async function listOpenCodeSessions(cwd?: string): Promise<ClaudeSessionSummary[]> {
   try {
     const { baseUrl } = await ensureServer();
@@ -35,7 +52,7 @@ export async function listOpenCodeSessions(cwd?: string): Promise<ClaudeSessionS
         const updated = s.time?.updated ?? created;
         return {
           id: s.id,
-          title: s.title || '(untitled)',
+          title: isPlaceholderOpenCodeTitle(s.title) ? '(untitled)' : (s.title ?? '(untitled)'),
           cwd: s.directory ?? '',
           createdAt: new Date(created).toISOString(),
           updatedAt: new Date(updated).toISOString(),