[Feature]: Durable per-thread "never settle" pin — the existing "active" override is cleared by activity, so no thread can be kept permanently active

[iamtoled]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web

Problem or use case

Some threads are long-lived by nature — a release thread, an ops/monitoring thread, a thread with background watchers waiting on external events. For those, every automatic settle is noise: I have to un-settle again and again, and a settled thread visually reads as "done" when it very much isn't.

Settling has several independent triggers, and today I can opt out of none of them per-thread. From packages/client-runtime/src/state/threadSettled.ts (effectiveSettled): a merged/closed PR settles immediately; inactivity past autoSettleAfterDays settles; and per #5514 a thread can pick up a PR association it never asked for, which then drives its settle state.

The model already has the right primitive: settledOverride: "active", described in that file as "the explicit keep-active pin". But it is transient — the same comment notes it only "suppresses auto-settle until real activity clears it server-side". So un-settling a thread buys me exactly one turn before it settles again (this is likely the mechanism behind #5476).

Proposal

A durable per-thread pin (context menu on the sidebar row, or thread settings) — e.g. "Never settle" / "Keep active". A pinned thread:

• is never auto-settled by any trigger (inactivity, merged/closed PR, PR association)
• is not cleared by activity — only the user removes the pin
• never shows settle banners or prompts, but can still be settled manually if I explicitly choose to

Related

#4982 asks for a global toggle on the merged/closed-PR rule; this is the per-thread complement that also covers the inactivity trigger. See also #5476 and #5514.

[iamtoled]

Filed #5576 as the framing behind this request: standing/recurring threads (triage sessions, ops threads, release threads, research logs) are never "done" — they go quiet between bursts by design — so the whole Done/settle/unread lifecycle misfires on them. This durable pin is the smallest useful increment of that.