emulator: in-fork plasma display (serial2=plasma) window in the explode layout

Bring the pod's 128x32 plasma readout in-fork, completing the self-contained
glass cockpit -- no vPLASMA process, no pipe.

- serialplasma.{cpp,h}: CSerialPlasma, a serial<n>=plasma backend that parses
  the game's ESC P graphics stream (L4PLASMA streams whole changed rows;
  receive-only, no replies) into a 128x32 1bpp framebuffer. Transcribed from
  vPLASMA's PlasmaProtocol + VPlasmaDevice (graphics path); the factory
  text-mode/fonts aren't used by the game and aren't rendered, but their escape
  operands are still consumed so the parser can't desync. Seam PLASMA_GetFrame()
  for the renderer.
- vpxlog.cpp: draw the framebuffer as an amber-on-black window in the explode
  layout, lazily created once a plasma port exists, parked centered under the
  lower-left MFD (VPX_PLASMA="x,y,w,h" overrides); WS_EX_NOACTIVATE so it can't
  steal DOSBox focus.
- Register SERIAL_TYPE_PLASMA (serialport.h/.cpp, dosbox.cpp -- documented in
  the vpx-device README step 3d, since those stock files live in the git-ignored
  src tree).
- Confs: serial2 in the _rio confs + deploy templates switches from
  namedpipe pipe:vplasma to the in-fork plasma.

Live-validated 2026-07-24. Real pods keep directserial realport:COM2; the
standalone vPLASMA app keeps namedpipe pipe:vplasma.

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

emulator/vpx-device/vpxlog.cpp

@@ -1728,6 +1728,30 @@ static void pal_draw(HDC dc, int g, int cw, int ch, bool dump) {
     SwapBuffers(dc);
 }
 
+/* ---- in-fork plasma display (serial=plasma) --------------------------------
+ * Render serialplasma's 128x32 1bpp framebuffer (16 bytes/row, MSB=leftmost)
+ * as an amber-on-black window in the explode layout. Seam = PLASMA_GetFrame
+ * (returns false when no serial=plasma port -> no plasma window). */
+extern bool PLASMA_GetFrame(uint8_t out[512]);
+
+static void draw_plasma(HDC dc, int cw, int ch, const uint8_t *fb) {
+    static unsigned char img[128 * 32 * 3];
+    for (int y = 0; y < 32; y++)
+        for (int x = 0; x < 128; x++) {
+            int lit = (fb[y * 16 + (x >> 3)] >> (7 - (x & 7))) & 1;
+            unsigned char *d = &img[(y * 128 + x) * 3];
+            if (lit) { d[0] = 255; d[1] = 150; d[2] = 30; }   /* amber plasma glow */
+            else     { d[0] = 8;   d[1] = 4;   d[2] = 0; }    /* near-black glass  */
+        }
+    glViewport(0, 0, cw, ch);
+    glClearColor(0, 0, 0, 1); glClear(GL_COLOR_BUFFER_BIT);
+    glDisable(GL_DEPTH_TEST); glDisable(GL_TEXTURE_2D); glDisable(GL_LIGHTING);
+    glPixelZoom((float)cw / 128.0f, -(float)ch / 32.0f);   /* scale + flip y */
+    glRasterPos2f(-1.0f, 1.0f);
+    glDrawPixels(128, 32, GL_RGB, GL_UNSIGNED_BYTE, img);
+    SwapBuffers(dc);
+}
+
 /* ---- click-to-press: map a click in a head window to a RIO button ----------
  * Mirrors the bezel geometry (draw_mfd_bezel / draw_radar_bezel): returns the
  * RIO address under (mx,my) in client coords, or -1 for a non-button click.
@@ -1913,6 +1937,7 @@ static DWORD WINAPI rt_main(LPVOID) {
     static const int ex_y[10] = { 560, 0,0,0,0, 560,  560,   20,  20,  20 };
     HWND pwnd[10]; HDC pdc[10]; HGLRC pgl[10];
     bool phave[10];
+    HWND pl_wnd = NULL; HDC pl_dc = NULL; HGLRC pl_gl = NULL; bool pl_have = false;  /* plasma window */
     int slot = 0;                        /* debug-grid position counter */
     for (int g = 0; g < NWIN; g++) {
         phave[g] = false;
@@ -1979,6 +2004,32 @@ static DWORD WINAPI rt_main(LPVOID) {
             RECT cr; GetClientRect(pwnd[g], &cr);
             pal_draw(pdc[g], g, cr.right, cr.bottom, dump);
         }
+        /* in-fork plasma window (explode only): appears once a serial=plasma
+         * port exists; lazily created below the layout, then rendered live. */
+        if (explode) {
+            uint8_t pfb[512];
+            if (PLASMA_GetFrame(pfb)) {
+                if (!pl_have) {
+                    int pw = 512, ph = 128, px, py;
+                    if (phave[5]) {   /* park centered just under the lower-left MFD (g5) */
+                        RECT r; GetWindowRect(pwnd[5], &r);
+                        px = r.left + ((r.right - r.left) - pw) / 2;
+                        py = r.bottom + 6;
+                    } else { px = 84; py = 1070; }   /* explode-layout fallback */
+                    env_rect("VPX_PLASMA", &px, &py, &pw, &ph);
+                    pl_have = make_gl_window("Plasma display (128x32)", pw, ph, px, py,
+                                             false, &pl_wnd, &pl_dc, &pl_gl);
+                    if (pl_have)  /* don't steal foreground from DOSBox */
+                        SetWindowLongPtrA(pl_wnd, GWL_EXSTYLE,
+                            GetWindowLongPtrA(pl_wnd, GWL_EXSTYLE) | WS_EX_NOACTIVATE);
+                }
+                if (pl_have) {
+                    wglMakeCurrent(pl_dc, pl_gl);
+                    RECT cr; GetClientRect(pl_wnd, &cr);
+                    draw_plasma(pl_dc, cr.right, cr.bottom, pfb);
+                }
+            }
+        }
         /* explode mode: once the DOSBox main screen exists, park it
          * centered under the Division window (one-shot; user can move it
          * afterwards). */