test_spinner_elapsed_format_is_fixed_width_to_reduce_wrap_jitter derived
_tool_start_time from the live time.monotonic() clock (now - 65.2 / now - 9.2).
monotonic()'s epoch is arbitrary — on a host where monotonic() < 65.2 (fresh
subprocess on a freshly-booted CI runner) the start time went negative, the
(t0 > 0) guard in _render_spinner_text() dropped the '(elapsed)' suffix, and
short.split('(',1)[1] raised IndexError: list index out of range. Deterministic
given a small clock, so it would keep flaking, not clear on rerun.
Pin time.monotonic to a fixed 1000.0 and offset _tool_start_time from it so both
the <60s and >=60s paths always render the elapsed suffix regardless of the
runner's monotonic epoch.
Pre-existing main flake (surfaced in CI test slice 1/8).
