Capture a chosen keyboard's keys without window focus (Raw Input)

The WinForms focus path only sees keys while vRIO is foreground and can't
tell one keyboard from another, so vRIO went deaf the moment the sim took
focus. The new "Capture keyboard" picker in the Input panel taps one
physical keyboard through the Win32 Raw Input API (RIDEV_INPUTSINK) and
routes its keys to the panel even in the background — the input-side twin
of the lamp mirror writing that keyboard's LEDs under the same condition.

Raw Input observes without intercepting, so keys still reach the focused
app; the picker defaults to "All keyboards (focus only)", preserving the
prior focus-bound behavior, and only registers Raw Input while a specific
device is selected. While capturing, the focus path stands down but still
swallows bound keys so they can't click panel buttons.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -48,6 +48,17 @@ controls:
   F1–F6 / F7–F12 = the Secondary / Screen columns, numpad = internal
   keypad (hex keys on the operators), arrows + Space = hat + main, with
   ABXY / dpad / shoulders on the pad's named buttons.
+- **Capture one keyboard in the background** (*Capture keyboard* picker in the
+  Input panel): by default keyboard input follows the focused window, so vRIO
+  goes deaf the moment the sim takes focus. Selecting a specific keyboard
+  instead taps it through the Windows **Raw Input** API (`RIDEV_INPUTSINK`), so
+  its keys drive the panel *while the game has focus* — the input-side twin of
+  the lamp mirror writing that keyboard's LEDs under the same condition. Raw
+  Input observes without intercepting: the keystroke still reaches the focused
+  app, so this is meant for a keyboard *dedicated* to the panel, not the one you
+  also type on. Leaving the picker on *All keyboards* keeps the plain
+  focus-only behavior. (No package identity needed — unlike the lamp side, this
+  is a plain Win32 tap.)
 
 ## Wire behavior