vmsig: management daemon, runtime endpoint lifecycle, roster, discovery, in-tree drivers, packaging

- core: runtime attach/detach of a per-endpoint adapter trio (runtime-safe add_adapter + vmsig_core_detach_endpoint, deferred reap)
- roster: VMSIG_EV_ROSTER + CAP_ROSTER, retained per-endpoint and replayed to late subscribers
- discovery: inotify trigger dir, vmid/endpoint slot allocator, host probe; vmsigd daemon with config + per-uid admission
- input driver and vgpu perception built in-tree; vgpu perception as a separate library
- memctx: own the supplied ro_fd (closed at detach)
- deb packaging: install rules, systemd unit, tmpfiles, default config

include/vmsig_event.h

@@ -63,6 +63,11 @@ typedef enum {
     /* --- UP: cursor (vgpu sensor; emitted by the vgpu-perception shell-as-control) --- */
     VMSIG_EV_CURSOR_STATE  = 37,  /* cursor position/visibility; inln=vmsig_cursor; cap OBSERVE|INPUT */
 
+    /* --- UP: VM roster (inventory coherence; daemon-originated, source=CORE) --- */
+    VMSIG_EV_ROSTER        = 38,  /* which VM occupies this endpoint: inln=vmsig_roster
+                                   * {vmid,state,action,name}, endpoint in the header; retained
+                                   * per-endpoint + replayed to late subscribers; cap ROSTER */
+
     /* --- UP: input/lifecycle ack (INPUT seam) --- */
     VMSIG_EV_ACT_ACK       = 48,  /* down-command completed (ok/err)         */
     VMSIG_EV_VM_LIFECYCLE  = 49,  /* power/lifecycle state report            */