Sidebar: fix scrollbar artifacts, keep sessions with pending work "running"

[pufit]

Three sidebar fixes from one report: a stray white dot, a horizontal scrollbar, and sessions dropping out of "Running" the moment their turn ended.

1. The white dot in the panel corner

index.css styles the scrollbar, its track and its thumb — but never ::-webkit-scrollbar-corner. Where a horizontal and a vertical scrollbar meet, WebKit painted that square with its own near-white default: a bright dot on a dark panel. Now transparent, like the track.

2. The horizontal scrollbar

Not cosmetic — a sizing bug. The ... load-more row was w-full plus mx-1, i.e. 100% + 8px, so the list overflowed by exactly those 8px (measured live: clientWidth 233, scrollWidth 241). Sized to calc(100% - 0.5rem), and the list is pinned to overflow-x-hidden: it only ever scrolls vertically and rows truncate, so nothing was reachable only by scrolling sideways.

3. Sessions with pending work stay "running" — and stay put

A session that scheduled a wakeup, or left a background job in flight, is not idle: it will pick itself back up. Two problems today:

• the moment its turn ended it fell out of the pinned Running group, and
• when the continuation landed, the assistant message bumped updated_at and yanked the session to the top of the list — reordering the panel for work the user never triggered.

Each row (and each session_running event) now carries two live bits:

field	source	meaning
pending_wakeup_at	session_wakeups, status='pending'	fire time of the one wakeup a session can have pending
has_background_tasks	the engine's per-session background-task registry	run_in_background Bash/Agent work still live in its CLI

A row with either is parked: it stays in the Running group and shows a violet pulse instead of the emerald one, so "working right now" still reads apart from "will resume on its own". Violet was the only free hue — blue is awaiting your input, orange review loop needs you, emerald running, red error, yellow stopped, accent unread. A tooltip names what it is waiting on (Background job running / Scheduled wake-up at 03:24 PM). Ranked below the error dot on purpose: a failed turn must not be masked by the background work it left behind.

Shipping both bits with the transition (not just on the list route) matters because the client deliberately skips the list refetch for the active session.

updated_at is now frozen for turns nobody asked for — internal=True runs (fired wakeup, restart continuation, star hook) and autonomous drains (a background task settling). The message row is still recorded and message_count still advances; only the sidebar's sort key is left alone. A turn the user actually sent bumps it as before.

Notes

• GET /api/sessions/search was duplicating _decorate inline; it now calls it, so search rows get the same treatment (including review-loop state) for free.
• Non-active sessions' background-task state is eventually consistent: background_tasks_update is broadcast on the session channel only, so a task that settles without triggering a continuation turn leaves the dot up until the next list refresh. Making that event global would close it — deliberately out of scope here.

Testing

• pytest tests/ — 3351 passed (15 new in tests/test_parked_sessions.py: the updated_at freeze at the store level and through feed ordering, the engine's pending-work lookup + broadcast payload, and the two fields on every sidebar list route).
• npm test — 114 passed (5 new for the client handler that applies the fields).
• npm run lint — unchanged (148 pre-existing problems before and after).
• Verified in the browser: the 8px overflow and the corner dot are gone; parked rows render violet inside Running, clearly distinct from the green ones.

Generated by Nerve

[alex-clickhouse]

I think it would be better to add bump_updated_at as a param to run() instead of overloading internal here. A couple of things that won't be bumped, when I think they should:

• Starring a session, which is marked internal:

  nerve/nerve/gateway/routes/sessions.py

  Line 483 in a587b06

  source="web", internal=True,

• Waking up a run-later task:

  nerve/nerve/cron/service.py

  Line 1352 in a587b06

  internal=True,

Both of those are user-requested actions that should bump updated_at.

Alternatively, we could just explicitly bump updated_at at both of those sites and leave the internal check as it is?