the sparklines were stretched across the whole gantt bar, but the profiler
wraps a SINGLE step (.github/actions/profile runs it between start/stop), so
on a job dominated by checkout + uv sync + post-job cleanup the samples only
describe a slice in the middle. reproduced: a 30s profile inside a 100s job
whose profiled step ran t=60..90 drew at left 0% width 100% instead of
left 60% width 30% — putting a cpu spike visually under a step that never ran.
the profile json had no wall-clock anchor to place it with, only duration_s,
so emit started_at/completed_at as iso-8601 utc in the same shape as github's
job timestamps. monotonic() still drives the sampling loop (immune to clock
steps); the timestamps are purely for placement.
_profile_window_pct() converts that window into bar-relative percentages and
both overlay states now use it — the expanded holder directly, the collapsed
strip via a .res-clip wrapper so its 100%-width is relative to the window
rather than the bar. the two states are asserted to agree on the x-axis.
falls back to the full bar, i.e. exactly today's behaviour, when the profile
predates these fields, when the timestamps don't parse, or when the window
doesn't overlap the job at all (clock skew between the runner writing the
profile and github's timestamps). a profiler that outran the job's
completed_at is clamped to the bar, and a sub-percent window keeps a 0.5%
hairline so it can't collapse to invisible.
7 new tests. verified they discriminate: forcing the old always-stretch
behaviour fails 4 of them, while the 3 fallback tests keep passing since
full-bar is what they want. tests/ci 145/145.
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