[client] input: synchronize host lock state over LGMP

Cache native keyboard lock state across input-provider transitions and
reconcile it with HID LED feedback over LGMP.

Project raw and corrective lock-key transitions through the reliable
input FIFO, defer correction until outstanding transitions settle, and
recover from delayed or missing feedback without double toggling.

client/include/interface/input.h

@@ -69,6 +69,8 @@ typedef struct LG_InputOps
   bool (*keyUp)(void * opaque, int key);
   bool (*keyboardLEDs)(void * opaque, bool numLock, bool capsLock,
       bool scrollLock);
+  /* Cancel any queued host-to-guest lock-state reconciliation. */
+  void (*keyboardLEDsReset)(void * opaque);
 
   bool (*mouseMotion)(void * opaque, int32_t x, int32_t y);
   /* Position is in guest pixels and must be within the supplied dimensions. */