feat: remove legacy OpenCode runtime

Cut product flows over to Coding/Pi and retain only the migration-owned v1 boundary. Promote supported native optional packages because electron-builder omitted pnpm transitive optional closure from the packaged ASAR.

electron/api/routes/coding-projects.ts

@@ -114,6 +114,16 @@ export async function handleCodingProjectRoutes(
       });
       return true;
     }
+    if (url.pathname === '/api/coding/projects/legacy-conversation-notice/acknowledge'
+      && req.method === 'POST') {
+      const body = await parseJsonBody<{ projectId?: string }>(req);
+      sendJson(res, 200, {
+        snapshot: publicProjectSnapshot(
+          await projects.acknowledgeLegacyConversationNotice(body.projectId ?? ''),
+        ),
+      });
+      return true;
+    }
     if (url.pathname === '/api/coding/projects/conversations' && req.method === 'GET') {
       sendJson(res, 200, {
         conversations: await conversations.listConversations(