saved sessions: replace transient history with persistent DB storage and auto-save

- Add saved_sessions table and CRUD endpoints (save, list, resume, update, delete)
- Save is instant (no LLM summarization), stores exact conversation with tool calls
- Resume loads full message history into chat UI, sends transcript to agent on first message
- Auto-save updates DB after every agent response once a session is saved
- Delete old filesystem-based session/group management (sessions router, useChatSessions, useChatGroups)
- Clean up ChatHeader, SessionList, ChatDetailPanel for saved sessions flow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/api/scrape/scrape.ts

@@ -30,10 +30,9 @@ export const scrapeRouter = createRouter();
 
 scrapeRouter.post('/', async (ctx) => {
   const user = ctx.get('user');
-  const { url, sessionId, provider } = ctx.get('body') as {
+  const { url, sessionId } = ctx.get('body') as {
     url: string;
     sessionId?: string;
-    provider?: 'claude' | 'pi-mono';
   };
 
   if (!url) return ctx.json({ error: 'url is required' }, 400);
@@ -140,9 +139,9 @@ scrapeRouter.post('/', async (ctx) => {
     let attachmentId: string;
     let saveDir: string;
 
-    if (sessionId && provider) {
+    if (sessionId) {
       attachmentId = `${slug}.html`;
-      saveDir = getAttachmentsDir(user.email, provider, sessionId);
+      saveDir = getAttachmentsDir(user.email, sessionId);
     } else {
       attachmentId = `${crypto.randomUUID()}.html`;
       saveDir = getTmpAttachmentsDir(user.email);