[AUTOMATED] fix(status): a dead worker printed 'running' — say DEAD

[mahaloz]

Found by round 4's captain, which wrote in its own notes that it had checked the
builders with ps, "not with status.py, whose stale_s only ticks on a phase change
and still lists b-r4-function-disasse as running". It was right, and it had to work
around the tool this loop gives it for exactly this question.

stale_s is now - updated_at, and updated_at moves on a state update, i.e. on a
PHASE CHANGE -- not on any sign of life. Neither status module calls os.kill, so
nothing ever asks whether the pid exists. reap() does ask, but only past
stale_seconds (1800) and only when something calls it. So a worker that dies mid-phase
reads running with a growing counter for up to half an hour, and the operator cannot
tell it from one working hard on a long phase. One label, two very different states.

collect() now records alive from a kill(pid, 0): True, False, or None when no pid
was recorded or the check itself failed -- unknowable is not the same as dead, and
PermissionError means the process exists under another uid. The repipe table prints
DEAD in the status column when a row claims running and the pid is gone.

Verified by planting a running worker with pid 999999 in the inventory: the row prints
DEAD, and the inventory was restored afterwards. scripts.pipeline.status --json still
works, so the angr lane is unaffected. tools/repipe/smoke.sh 127/127.

Fourth instance of one pattern this session, and the last three were found the same way
-- a number checked for an unrelated reason. Provider refusals counted as kuna failures
(#419); un-refuted hypotheses indistinguishable from undecided ones (#420); a builder
budget cap indistinguishable from a broken build (#436); now a dead worker
indistinguishable from a busy one. Each time, a status collapsed two causes into one
label, and nothing failed loudly.

Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com

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https://claude.ai/code/session_01YcFmfZndNjgfqLQVBZCdkY