batch4.1-5.1: dedup audit, archive 400 fix, sidebar Delete, landing-page enrichment, auto-name tool-call fix

- Fastify global empty-JSON-body parser fixes archive/unarchive/stop 400s
- Removed redundant local sessionEvents.emit at all 5+2 sites with server-side WS publishers; added dedupe guards in useSidebar/Workspace/Project handlers
- Sidebar session right-click adds Delete (destructive) with confirm Dialog
- Session.tsx navigates away on session_deleted/session_archived for the active session
- SessionLandingPage chat rows show message_count, effective_context_tokens, last_message_preview via LATERAL joins on GET /api/sessions/:id/chats
- Workspace.tsx pane drag-to-reorder using native HTML5 events (no new deps)
- CompactCard: Copy toast, Send-to-chat with target chat name, empty-state in share popover, Re-run button
- auto_name.ts: filter count gate and assistant-fetch by content <> '' so tool-call assistant rows don't trip the once-and-only-once guard
- Adds CLAUDE.md and apps/web/src/lib/format.ts

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/api/types.ts

@@ -33,6 +33,10 @@ export interface Chat {
   status: ChatStatus;
   created_at: string;
   updated_at: string;
+  // Populated by GET /api/sessions/:id/chats only.
+  message_count?: number;
+  last_message_preview?: string | null;
+  effective_context_tokens?: number | null;
 }
 
 export type MessageRole = 'user' | 'assistant' | 'tool' | 'system';