input: modern dual-stick controller layout (Xbox re-release scheme)

Steam Deck target. LS move/strafe + RS look + RT fire + LT aim were
already in place (D194/D238 naturalPitchMode); this completes the
scheme with shoulder weapon cycling per the console re-releases:
RB rising edge = next weapon, LB rising edge = previous weapon.

Cycling rides the game's own A-line formulas (bondview2.c
weaponForwardOffset/weaponBackOffset): a fresh A edge cycles forward;
A+Z presented on the same tick cycles backward -- the identical trick
the mouse-wheel path uses (D223), which also guarantees no stray shot
(triggerOn is gated off while invButtons is held). Edges are emitted
for exactly one poll so holding a shoulder cannot latch A and block
firing; both are suppressed in menu mode where A means select.

A/X = action/use, B/Y = crouch/cancel (unchanged); LB no longer maps
to lean. README controls table + release notes updated.

.github/release-notes.md

@@ -23,6 +23,9 @@
 - **QoL**: F10 in-game options overlay (fullscreen, resolution, frame cap,
   MSAA, texture filtering, FOV/draw distance, sensitivity), mute-on-focus-loss,
   F12 screenshot.
+- **Modern dual-stick controller layout** (the scheme used by the console
+  re-releases): left stick move/strafe, right stick look, right trigger fire,
+  left trigger aim, A/X use, B/Y crouch/cancel, **RB/LB cycle weapons**.
 - **Linux / Steam Deck**: the Linux bundle now ships its own SDL2 — it runs
   as-is on any distro, and sideloads onto a Steam Deck with nothing installed.