[Feature]: Let agents set a short status line on their sidebar thread row (t3_thread_set_status)

[orgal-clearsai]

Area

apps/server (t3-code MCP toolkit), apps/web sidebar thread rows, packages/contracts

Problem or use case

I run long-lived "manager" threads: one agent per epic that wakes on a timer, checks CI and pull requests, answers questions, and waits for others. The sidebar shows that a thread is working, monitoring, waiting for input, or done. It doesn't show where the thread is in its work. To find out, I have to open each thread and scroll to its last message.

What I want on each row is one short line the agent sets itself, for example:

• 2 PRs in review · next check 07:27
• waiting on CI for #2947
• blocked: needs merge approval

Proposal

• Add an MCP tool such as t3_thread_set_status({ text }). It sets a short line (≤ ~60 chars) on the current thread, and text: null clears it.
• The sidebar renders the line under the title, muted, truncated with an ellipsis, and shows the full text on hover.
• The line is ephemeral. It is cleared automatically when the thread settles, or optionally when a new user message arrives, so a stale status never sticks.
• The line is separate from the title. The title stays what the thread is about; the status line is where it is right now.

How this differs from existing requests (I checked)

• Allow agents to rename the current thread #11968, [Feature]: Expose thread rename to agents via the t3-code MCP server (t3_thread_rename) #11564, [Feature]: Let the agent update its thread title once the work is actually decided #7333 (agents rename the thread / update its title): these change the title permanently. This request is a separate, ephemeral progress line, and the title stays put.
• [Feature] Show actual agent progress in iOS Live Activities and Android Live Updates #14114 (live agent progress on iOS/Android Live Activities): that is automatic activity text on mobile ("Editing X"). This request is a line on the desktop/web sidebar that the agent writes itself, which works even while the agent is idle between scheduled checks.
• Supported read-only thread status stream for external tools (OpenDeck use case) #10929 (read-only status stream for external tools): that one exports status. This one lets an agent set it.

Alternatives considered

• Renaming the thread to carry status loses the real title, and churns the title on every check.
• Linking PRs (link_pull_request) shows PR state only, not the agent's own progress.