Stage 4 increment 1: per-device WIREBIND tracking, fixing a real multi-identity detach leak (FABRIC-3.md §XXVIII Stage 4)

capsule_wirebind_unclean_detach()/eject() tracked "the attached identity"
as a single global, correct for the console-pairing UX (one physical
console) but wrong for detach safety: since §XV/§XVI proved multiple
identities genuinely live simultaneously via this same attach path, every
attach after the first silently overwrote the singleton, so an unclean
detach of any but the most-recently-attached identity was silently
ignored -- that VM leaked forever, no trace in the log.

Adds a per-device live-identity table, separate from the (unchanged)
console-pairing singleton, so unclean-detach resolves any attached
device to its own identity. Sized off messaging.4th's own VM-MAX (16)
minus Tripod's 3 reserved slots, not an invented number. Corrects the
stale "single-USB-device constraint" doc claim in capsule_wirebind.h,
false since §XV/§XVI.

Groundwork for Stage 4's real deliverable (WIREBIND VMs as switch-signal
participants) -- this increment only fixes detach targeting; switch-
signal registration is next.

Verified clean on all 3 architectures (no WIREBIND attach happens in a
plain boot, so this is a regression check on the existing Tripod-only
path; live multi-identity verification comes with the switch-signal
registration increment).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BWpNjdwPtFLuVLaAq44L9K

This commit is contained in: