A running run names its step

[czpython]

The bug

A running build showed "Working…" where it should have said "Generate plan". The INFO panel on the same screen said "Generate plan" — so the name was right there, one component away.

Two different things render, and only one names the step:

• INFO panel → statusLine(status) → kindLabel(status.agent) → "Generate plan"
• Timeline row → activity.label → the phase → "Working…"

It only bites when a run has one call in flight, because the row folds the call into itself:

const collapseCalls = run.agentCalls.length <= 1

Folded, the call's own row is gone, so the name goes with it and the generic phase fills the gap. A second call splits the rows and the names come back — which is why this looks intermittent, and why it hides the step at exactly the moment there's only one thing happening.

The cause

SubjectActivity says what it is for:

"The running sub-phase the timeline can't show ("Building sandbox VM…")"

It exists for the gap before an agent call exists. But the phase map broke its own contract:

"provisioning_vm": "Building sandbox VM…"   # the timeline genuinely can't show this
"agent_running":   "Working…"                # the timeline shows this, and better

agent_running reported a label for the one case the timeline covers, and reported it worse. Its only real effect was handing the frontend a plausible generic string to render by mistake.

The change

Backend — agent_running maps to nothing. SubjectActivity is infra-only again, so there is no generic label available to render wrongly. The phase itself still fires; it's what clears provisioning_vm.

Frontend — a running run's sub-line reads its running call's label when the calls are folded in, and the infra phase otherwise. Fixing the good option to win would have left the bad one reachable; removing it makes the correct thing the only thing.

The sub-line moves out of a five-branch ternary into runSubLine in statusLine.ts, which already declares itself the home of the extension's words. STATE_LABEL went with it — it had no other caller — so WorkItemPage loses a constant.

Verification

tsc, eslint, ruff clean. Six new cases in statusLine.test.ts (14 pass): the folded step names itself; split calls leave the name to their own rows; the infra phase still shows before an agent starts; and parked/failed/scheduled are unchanged. The test factories build real RunSummary/AgentCallSummary values with no as casts, so they typecheck against the actual shapes.

Five backend files are unformatted on main and untouched here; left alone rather than padding the diff.