vPLASMA: companion app emulating the cockpit plasma display

The cockpit's second serial device joins vRIO: the 128x32 dot-matrix
plasma on COM2 (9600 8N1) that the game draws mission text and status
graphics on. VPlasma.App opens the device end of a COM port, decodes
the display's command stream, and renders the matrix in plasma orange.

The command set is recovered from two Tesla 4.10 artifacts: the game's
driver (L4PLASMA.CPP — ESC P packed-bitmap row writes, ESC G 0 cursor
hide at boot) and the factory test tool PLASMA.EXE, whose data segment
pairs each command literal with its printf description (BS/HT/LF/VT/CR
motion, ESC @ clear, ESC L home, ESC G cursor, ESC K fonts, ESC H
attributes: intensity/underline/reverse/flash). Text renders through
the classic public-domain 5x7 set standing in for the lost ROM glyphs;
fonts 0-3 give 21x4 cells, fonts 4-7 the doubled 10x2. A Self test
cycles banner/charset/graphics pages through the same parser the wire
feeds, and the wire log shows every decoded command.

Verified end-to-end over the second com0com pair (host writing COM2,
vPLASMA listening on COM12). The verify skill gains the cross-process
combo-box lesson: string-carrying CB_* messages hang across processes,
so select ports by locally computed index via CB_SETCURSEL.

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

.claude/skills/verify/SKILL.md

@@ -10,8 +10,16 @@ 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
+# exe: src\VPlasma.App\bin\Debug\net48\VPlasma.App.exe   (companion display)
 ```
 
+Everything below applies to vPLASMA too. Its serial path can be tested
+end-to-end on this machine: vPLASMA opens **COM12**, the script plays the
+game writing **COM2** (second com0com pair; vRIO/RIOJoy use COM1⇄COM11).
+Killing a writer mid-stream can leave stale bytes queued in the com0com
+buffer — the next session's byte counter will run high; re-run clean
+before trusting counts.
+
 ## Driving the GUI without touching the user's desktop
 
 This is the user's live desktop — **never** use SetForegroundWindow +
@@ -33,6 +41,14 @@ VS Code and your clicks land in the user's windows. Instead:
   (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).
+- **Combo boxes** (COM port pickers): string-carrying messages
+  (`CB_FINDSTRINGEXACT`, `CB_GETLBTEXT`) do **not** marshal across
+  processes — the SendMessage hangs. Compute the item index locally
+  (both apps fill from `SerialPort.GetPortNames()` sorted
+  OrdinalIgnoreCase) and send index-only `CB_SETCURSEL`; the apps read
+  `SelectedItem` lazily so no CBN_SELCHANGE notification is needed.
+  Find the combo child HWND via EnumChildWindows + GetClassName
+  containing `COMBOBOX` (UIA ClassName "ComboBox" doesn't match).
 - 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`.