What: holdTicker({show, clear}) in update-marker-gate.ts owns a wait's hold
state machine (keep the probe's latest held state, consume it per poll,
show it after the unbroken grace, clear otherwise); the primary boot wait
in main.ts and waitForPoolUpdateClearance both use it, replacing the
copy-pasted held/holdGraceClock/show-or-clear code. UpdateHoldWire moves to
electron/update-hold-types.ts and src/global.d.ts re-exports it instead of
hand-mirroring it as DesktopUpdateHold (renderer users take UpdateHoldWire).
Why: the hold state machine was duplicated between the two waits and the
wire type had two definitions that could drift. c8fc9ae5b4a/b5e2fc62e3b had
already moved the controller ({show, clear} + registerUpdateHoldIpc) and the
pool wait out of main.ts and replaced the positional optionals with
updateGateDeps({onLiveMarker, onHeld, onOverride}); this finishes the split.
main.ts: 19835 -> 19823 lines (origin/main 19864). Same calls, same order.
Review: kshitijk4poor 5411222842 (shape: main.ts growth, duplicated hold
state machine, UpdateHoldWire mirror).
Tests: update-marker-gate.test.ts holdTicker (red on start sha: no export).
7b27ff08a6