Fix the backtick crash (a /FORCE-hidden linkage bug) + backtick = view toggle

The crash (any typed key in a glass session; found via the backtick report):
the merge-reconciliation stand-down declared extern BTRIODevicePresent at
BLOCK scope inside the extern-C BTInputSuppressKey -- the declaration
inherited C linkage, _BTRIODevicePresent went UNRESOLVED, and /FORCE bound
the call to garbage (cdb: wild call into Sensor::DefaultData from
LBE4ControlsManager::Execute's suppression check).  The tolerated-LNK2019
batch hid the new unresolved external -- the exact CLAUDE.md /FORCE trap.
Fix: the extern moved to file scope (C++ linkage); link verified clean of
_BTRIODevicePresent.

Backtick feature (per Cyd: backtick = 1st/3rd person): PadRIO edge-detects
VK_OEM_3 in its poll (focus-guarded, message-path-free) and the mech4 view
block consumes it beside the V action (which stands down with the binding
engine in glass mode).  Verified live: two real presses -> [view] COCKPIT
eyepoint -> [view] external chase, game alive.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

game/reconstructed/mech4.cpp

@@ -2721,6 +2721,19 @@ void
 						BTSetViewInside(sViewInside);
 					}
 					sPrevV = vNow;
+#ifdef BT_GLASS
+					// The glass backtick toggle (PadRIO edge; the V action
+					// stands down with the binding engine in glass mode).
+					{
+						extern int BTPadViewToggleEdge(void);
+						while (BTPadViewToggleEdge())
+						{
+							sViewInside = !sViewInside;
+							extern void BTSetViewInside(int inside);
+							BTSetViewInside(sViewInside);
+						}
+					}
+#endif
 
 					// RETICLE = SCREEN CENTER (task #58 correction, supersedes the
 					// task #39 "body-mounted view" model): the CAMERA yaws with