mission-phase-timers.md left 180 open as "a limit and a warning
threshold is the obvious reading, but not established". Reading
sub_822639B8 -- ScriptPhase::Update 0x82263528, same dt as the
stopwatch bank -- settles it the other way:
if running: [+304] += dt
if armed: [+308] -= dt while [+308] > 0
else [+312] -= dt, clamped at 0
[+312] is never compared with [+308]; it is decremented, and only in
the A<=0 arm. Two sequential countdowns. Disc-wide the second
argument is 180 in all 29 timer_set sites while the first varies
(600 x19, 1200 x8, 900, 1800).
Built-ins 123-127 are vtable slots 90-94 on five scalars at
[phase+304..320]. 125 and 126 have ZERO call sites in all 28 scripts:
the script arms, starts and stops this clock but never reads it.
Corrects mission-phase-timers.md, which merged this clock with
stopwatch 0 -- timer_resume starts [+304], set_flag(0) one instruction
later starts the stopwatch the timeline's kind=0 reads.
Docs only; all seven ISL artefacts regenerate byte-identical.
a09c9e6517