Project verify skill: drive the GUI via PostMessage + PrintWindow

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

.claude/skills/verify/SKILL.md

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+---
+name: verify
+description: Build, launch, and drive the vRIO WinForms app to verify changes at the GUI surface — screenshots via PrintWindow, input via PostMessage, no focus stealing.
+---
+
+# Verifying vRIO changes
+
+Build + tests (tests are CI's job; run the app for verification):
+
+```powershell
+dotnet build vrio.sln -v q -nologo          # Debug
+# exe: src\VRio.App\bin\Debug\net48\VRio.App.exe
+```
+
+## Driving the GUI without touching the user's desktop
+
+This is the user's live desktop — **never** use SetForegroundWindow +
+SendKeys/mouse_event: focus-stealing prevention leaves the app behind
+VS Code and your clicks land in the user's windows. Instead:
+
+- **Screenshots**: `PrintWindow(hwnd, dc, 2)` (PW_RENDERFULLCONTENT) —
+  captures the window even when occluded. CopyFromScreen captures
+  whatever is on top; don't use it.
+- **Canvas input** (stick drags, cell clicks): PostMessage
+  `WM_LBUTTONDOWN/WM_MOUSEMOVE/WM_LBUTTONUP` straight to the canvas
+  child HWND. Find it by descending `RealChildWindowFromPoint` from the
+  form. Canvas geometry is compile-time constant (PanelCanvas.cs):
+  CellW=66, BoxXY = x 416..496, y 6..74 (X/Y stick box).
+  The **first** posted drag after launch can half-land (only the
+  button-down registers); do a throwaway drag first, then the measured
+  one, screenshot **while held** (spring-back recenters on up).
+- **Checkboxes/buttons**: WinForms controls expose no UIA TogglePattern
+  (they surface as bare Panes) and don't answer BM_GETCHECK — but
+  `SendMessage(hwnd, BM_CLICK, 0, 0)` works. Get the HWND from the UIA
+  element's NativeWindowHandle (find by Name).
+- Pattern that works: Add-Type user32 P/Invokes, Start-Process the exe,
+  drive via messages, PrintWindow screenshot to the scratchpad, kill
+  the process in `finally`.
+
+## Environment gotchas
+
+- Bindings load from `%APPDATA%\vRIO\bindings.txt` (the user's file),
+  not the built-in defaults — arrow keys are bound to Hat *buttons*,
+  not the joystick axis. Drive axes via the X/Y box.
+- A real XInput gamepad is connected on this machine ("Controller #1
+  connected"); the router only writes an axis when its composed value
+  changes, so a centered pad won't fight a canvas drag.
+- The wire readout (top center, green) shows `GetWireAxis` values —
+  joystick Y is natively negated on the wire (stick up = −80) unless
+  "Invert Y" is checked.