feat(input): drop absolute-pointer (ABS) support

ABS was glued onto device A alongside the keyboard and never worked right; it is
not needed in practice. Remove it entirely: device A is now keyboard-only, and
device B is the relative mouse (motion + buttons incl. middle + wheel). Drops the
ptr_mode model (one layout remains), VMCTL_EV_ABS/PTR_*, and the absolute axes.

The public input-kind enum keeps its numeric values (MOVE_REL=1, BTN=2, KEY=3,
SCROLL=4) so the wire stays compatible -- only MOVE_ABS (0) is removed and its
slot reserved; an unknown/0 kind is a no-op.

Bump 0.3.11.

src/adapter/vmhost/include/vmhost.h

@@ -10,7 +10,7 @@ typedef struct {
     const char* qmp_path;
     /* Host->guest input bridge: evdev node paths of the uinput devices (published by the input
      * seam). When non-NULL/non-empty, on reaching READY the seam adds an input-linux QMP object
-     * forwarding them into the guest (A=kbd+abs with grab_all, B=mouse). NULL/"" => no bridge
+     * forwarding them into the guest (A=keyboard with grab_all, B=relative mouse). NULL/"" => no bridge
      * (stub/tests are fail-closed). Pointers are borrowed from the stable per-endpoint home and
      * outlive the adapter. */
     const char* bridge_evdev_a;