/chat-workspace: live backend chat flow and scoped persistence

[rmusser01]

Parent tracker: #1239

Goal

Make /chat-workspace work as a live backend chat surface, not only a scaffolded route.

Current evidence

The page already routes through WorkspaceChatPanel and useMessageOption({ scope }), with workspace-id send guarding and stop-generation plumbing. The missing proof is a live, authenticated flow that covers model/persona selection, send, streaming, stop, error recovery, and scoped persistence.

Acceptance criteria

• Model selection is usable from /chat-workspace or clearly inherited through an adjacent shared control without leaving users stranded.
• Persona/assistant selection is usable from /chat-workspace or clearly inherited through an adjacent shared control.
• Sending a message with a hydrated workspace creates or resumes a workspace-scoped server chat.
• Streaming responses render incrementally and expose a working stop-generation control.
• Error recovery preserves the draft and staged context when a send fails.
• Workspace-scoped conversation history persists, reloads, and switches cleanly when users change workspaces.
• No send path can create a global or empty-workspace chat while workspace identity is still hydrating.

Verification target

Add focused unit/integration coverage plus a live-backend browser proof once the fixture from the coverage issue is available.

References

• Parent tracker: Epic: Complete Chat Workspace web UI implementation #1239
• Foundation PR: Add Chat Workspace web UI #1233
• Main area: apps/packages/ui/src/components/Option/ChatWorkspace/

[rmusser01]

Closed after PR #2595 merged.

Evidence from the merged branch:

• /chat-workspace now sends through the live backend via workspace-scoped server chat creation/resume.
• Message mirroring carries workspace scope for user, assistant, and image-event paths.
• Cached server chat ids are validated against the active workspace before reuse, preventing stale/global chat reuse.
• Streaming, stop-generation, send failure recovery, draft preservation, and staged context recovery are covered by the focused live-backend smoke.
• Local verification before merge included the Chat Workspace live-backend Playwright spec: 4 passed.