gig-log: the MIDI lens asks the kernel who it is wired to, on a clock

Zero control moves were logged for the whole 2026-09-24 set, and every
cheap check said fine. Two independent faults, both found by looking:

THE CHECK RAN ON TRAFFIC, NOT ON A CLOCK. The re-resolve lived inside
'for line in self._proc.stdout', so it only ran after a line ARRIVED. A
bound port that goes quiet blocks that iterator forever, and aseqdump does
not exit — so the loop parked on a blocking read from 01:01 through a
94-minute set. Now a timed select: the liveness question is asked every
UPGRADE_S whether or not the board said anything. The old test asserted
this the other way round, on the reasoning that running in the read loop
was 'cheap by construction: an idle surface costs nothing at all'. An idle
surface cost the gig. 'Costs nothing when idle' and 'notices when idle'
are the same code path and only one can be true.

A NAME AND AN ADDRESS ARE BOTH USELESS HERE. 38 hours after the set, 133:0
'ParVagues LCXL3' still resolved to that exact address under that exact
name — so neither 'is it gone' nor 'did it move' could see anything. What
happened is the third thing: lcxl3-driver restarted repeatedly between
00:34 and 10:27, and the kernel handed each new sequencer client the same
number. Our subscription died with the old one. Verified live: client 133
was 'Connecting To: 129:0, 14:0' and gig-log's aseqdump, client 135, was
not in the list.

So subscription_alive() asks the kernel's own wiring table, matching the
CHILD's pid — the same discrimination lcxl3-driver's board_link_alive
makes, for the same reason. It reads False on the real dead link and True
on SuperCollider, which is wired to the same port; 'cannot tell' is None,
never False, so a box where aconnect differs does not thrash.

gig-log status now names the binding, its subscription state and the
session's control-event count. It used to answer 'is it writing', which
was true and useless on the night the file grew at 1 Hz with nothing in
it. A dashboard that shows LIVE while a whole lens is dead is the green
check this rig has learned not to trust.

Note: tools/tests/test_one_tidal_parser.py fails at HEAD too, on
fold-orbits.py. Untouched here.

TODO.d/2026-09-25-post-gig-belt-and-braces.md

@@ -16,7 +16,7 @@ Each line pays off a `TODO_GIG` "NOT TONIGHT" entry or a loss measured in
 - [x] **2. Nothing checks record-arm.** `Tidal 08` sat at `rec-enable=0` all
       night; twelve tools audit faders, mutes, routing, ghosts, preload — none
       audit arm. Extend `check-mix.py`, add a `check-gig.py` probe.
-- [ ] **3. gig-log loses its MIDI address.** Bound seq port `133:0` at 00:59,
+- [x] **3. gig-log loses its MIDI address.** Bound seq port `133:0` at 00:59,
       never rebound; zero control moves logged for a 94-minute set. Probe now,
       rebind as its own change. (`TODO_GIG`: "gig-log loses its MIDI address and
       never looks for it again")