refactor(tabs): live Zero-synced tabs with workspace limits and UI polish

[AnishSarkar22]

Description

• Reworked the tab system so tabs store only lightweight pointers (id, type, entity id, workspace id) instead of persisting full server-owned snapshots, cutting over to a new v2 storage key.
• Added a resolver hook that joins tab pointers against Zero and derives titles/existence live, pruning a tab only when its row is absent and the query has confirmed completeness.
• Extended the Zero thread schema with title, visibility, and created-by, and added by-ids queries for threads (with per-thread authz: own thread or workspace-shared) and documents.
• Published the new thread metadata columns to the Zero publication via a new migration so titles and access filtering sync in real time.
• Removed the legacy tab migration and its test now that tabs use the pointer-only v2 shape.
• Rewired all tab consumers to resolved tabs: the tab bar renders from resolved data, the layout shell splits tabbed/untabbed panels behind a show-tabs flag and resolves document tabs via entity id plus live title, and the free layout renders untabbed.
• Reworked fallback navigation for pointer tabs, deriving URLs from entity/workspace ids and letting title and visibility resolve asynchronously.
• Dropped the title/visibility/has-comments snapshot arguments from tab sync in the activate-thread hook and the new-chat page effect.
• Added a configurable per-user workspace creation limit enforced on the backend with unit tests, and surfaced that limit to the frontend through types, API service, query atoms, cache keys, and limit-aware "add workspace" affordances across the create dialog, icon rail, and sidebars.
• Added a threads loading skeleton and relative timestamp formatting in the All Chats sidebar, backed by a shared date helper.
• Added a chats-click handler across sidebar components for improved navigation.
• Added cookie persistence for the playground sidebar collapsed state.
• Improved chat message loading-state handling and introduced a can-submit interface/logic to gate chat submission.
• Polished panel headers and controls across the citation, report, and artifacts panels, refined inline citations, and clarified the connect-agent dialog title.
• Refined the chat header's responsive styling and updated the automations loading skeleton.
• Swapped the document mention picker icon for better visual consistency.

Motivation and Context

FIX #

Screenshots

API Changes

• This PR includes API changes

Change Type

• Bug fix
• New feature
• Performance improvement
• Refactoring
• Documentation
• Dependency/Build system
• Breaking change
• Other (specify):

Testing Performed

• Tested locally
• Manual/QA verification

Checklist

• Follows project coding standards and conventions
• Documentation updated as needed
• Dependencies updated as needed
• No lint/build errors or new warnings
• All relevant tests are passing

High-level PR Summary

This PR refactors the tab management system to rely on real-time Zero synchronization for chat thread metadata instead of persisting full metadata in local storage. The tabs now store only lightweight pointers (entityId and workspaceId) that are resolved against Zero queries at runtime. Additionally, backend workspace creation limits are enforced with a new configurable MAX_WORKSPACES_PER_USER setting, and various UI improvements include better loading states, refined panel headers, improved date formatting, and visual polish across chat and sidebar components.

⏱️ Estimated Review Time: 1-3 hours

💡 Review Order Suggestion

Order	File Path
1	surfsense_web/atoms/tabs/migrate-tabs.test.ts
2	surfsense_web/atoms/tabs/migrate-tabs.ts
3	surfsense_web/atoms/tabs/tabs.atom.ts
4	surfsense_web/hooks/use-resolved-tabs.test.ts
5	surfsense_web/hooks/use-resolved-tabs.ts
6	surfsense_web/zero/schema/chat.ts
7	surfsense_web/zero/queries/chat.ts
8	surfsense_web/zero/queries/documents.ts
9	surfsense_web/zero/queries/index.ts
10	surfsense_backend/app/zero_publication.py
11	surfsense_backend/alembic/versions/175_publish_thread_metadata_to_zero.py
12	surfsense_web/components/layout/ui/tabs/TabBar.tsx
13	surfsense_web/components/layout/ui/shell/LayoutShell.tsx
14	surfsense_web/app/dashboard/[workspace_id]/new-chat/[[...chat_id]]/page.tsx
15	surfsense_web/hooks/use-activate-chat-thread.ts
16	surfsense_web/components/layout/providers/LayoutDataProvider.tsx
17	surfsense_web/components/layout/ui/sidebar/AllChatsSidebar.tsx
18	surfsense_web/components/assistant-ui/thread.tsx
19	surfsense_web/lib/chat/can-submit-chat.ts
20	surfsense_backend/app/config/__init__.py
21	surfsense_backend/app/routes/workspaces_routes.py
22	surfsense_backend/tests/unit/routes/test_workspaces_limits.py
23	surfsense_web/contracts/types/workspace.types.ts
24	surfsense_web/lib/apis/workspaces-api.service.ts
25	surfsense_web/atoms/workspaces/workspace-query.atoms.ts
26	surfsense_web/lib/query-client/cache-keys.ts
27	surfsense_web/components/layout/providers/FreeLayoutDataProvider.tsx
28	surfsense_web/components/layout/ui/icon-rail/IconRail.tsx
29	surfsense_web/components/layout/ui/dialogs/CreateWorkspaceDialog.tsx
30	surfsense_web/components/layout/ui/sidebar/MobileSidebar.tsx
31	surfsense_web/components/layout/ui/sidebar/Sidebar.tsx
32	surfsense_web/lib/format-date.ts
33	surfsense_web/components/citation-panel/citation-panel.tsx
34	surfsense_web/components/report-panel/report-panel.tsx
35	surfsense_web/features/chat-artifacts/ui/artifacts-panel.tsx
36	surfsense_web/components/assistant-ui/inline-citation.tsx
37	surfsense_web/components/new-chat/chat-header.tsx
38	surfsense_web/components/new-chat/document-mention-picker.tsx
39	surfsense_web/components/mcp/connect-agent-dialog.tsx
40	surfsense_web/app/dashboard/[workspace_id]/automations/components/automations-loading.tsx

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