feedback: plasma box, explicit fonts, and per-position text coalescing

Three endpoint gaps, found building the Descent 3 score overlay - the boxed
place|score field the original games drew over the callsign:

plasma box <x> <y> <w> <h> draws an outlined box with a blanked interior, the
overlay chrome, as one ESC P graphics write. The wire addresses whole bytes
horizontally, so the write covers the byte-aligned span containing the box and
clears span pixels outside it; documented, with 8-px alignment the advice.
Boxes queue FIFO with rows.

plasma text gains an explicit font: a third numeric token after the position,
with text still following, so `plasma text 2 2 7` still displays "7". Auto-fit
picks the font by LENGTH - short text always rendered large, and a "1" that
must fit a 12-px box simply could not be sent before. ResolvePosText
generalizes the legacy Score-font special case: 0 = auto, nonzero honored.

Text coalescing is now per position. The global rule - any queued text
superseded every other queued text - meant the documented two-field layout
(callsign top, score bottom) could not survive its own send burst: the second
field silently ate the first whenever both were queued. A newer text now
replaces only a queued text at the same (x,y).

15 new tests; 472 pass.

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

src/RioJoy.Core/Feedback/FeedbackRouter.cs

@@ -18,12 +18,13 @@ namespace RioJoy.Core.Feedback;
 /// profile-owned lamps for the same reason.
 ///
 /// Plasma writes are single-flight over a small bounded queue whose rules
-/// match what each command means: <c>text</c> coalesces (only the newest
-/// queued text survives — a flooding score updater shows the latest value),
+/// match what each command means: <c>text</c> coalesces per position (only the
+/// newest queued text at the same (x,y) survives — a flooding score updater
+/// shows the latest value, while other fields on the glass keep theirs),
 /// <c>clear</c> flushes everything queued before it, and bitmap <c>row</c>s
-/// are FIFO in arrival order (a frame is many rows; coalescing would tear
-/// it). The bound caps what a flooding client can queue against the
-/// 9600-baud display port.
+/// and <c>box</c>es are FIFO in arrival order (a frame is many rows;
+/// coalescing would tear it). The bound caps what a flooding client can queue
+/// against the 9600-baud display port.
 /// </summary>
 public sealed class FeedbackRouter
 {
@@ -111,6 +112,7 @@ public sealed class FeedbackRouter
             case FeedbackCommandKind.PlasmaText:
             case FeedbackCommandKind.PlasmaClear:
             case FeedbackCommandKind.PlasmaRow:
+            case FeedbackCommandKind.PlasmaBox:
                 DispatchPlasma(target, command);
                 break;
         }
@@ -172,20 +174,30 @@ public sealed class FeedbackRouter
                     break;
 
                 case FeedbackCommandKind.PlasmaText:
-                    // Only the newest text survives (a score updater shows the
-                    // latest value); queued rows keep their place.
+                    // Only the newest text FOR THE SAME POSITION survives (a
+                    // score updater shows the latest value). Texts at other
+                    // positions are other fields - the documented multi-field
+                    // layout (callsign top, score bottom) sends several in a
+                    // burst, and the original global coalescing ate all but
+                    // the last of them. Queued rows/boxes keep their place.
                     for (int i = _plasmaQueue.Count - 1; i >= 0; i--)
                     {
-                        if (_plasmaQueue[i].Kind == FeedbackCommandKind.PlasmaText)
+                        if (_plasmaQueue[i].Kind == FeedbackCommandKind.PlasmaText &&
+                            _plasmaQueue[i].X == command.X && _plasmaQueue[i].Y == command.Y)
                         {
                             _plasmaQueue.RemoveAt(i);
                             Interlocked.Increment(ref _dropped); // superseded before it ran
                         }
                     }
+                    if (_plasmaQueue.Count >= MaxPlasmaQueue)
+                    {
+                        Interlocked.Increment(ref _dropped);
+                        return;
+                    }
                     _plasmaQueue.Add(command);
                     break;
 
-                default: // PlasmaRow: strict FIFO — a bitmap frame is many rows
+                default: // PlasmaRow/PlasmaBox: strict FIFO — a bitmap frame is many rows
                     if (_plasmaQueue.Count >= MaxPlasmaQueue)
                     {
                         Interlocked.Increment(ref _dropped); // client outran the display
@@ -219,7 +231,10 @@ public sealed class FeedbackRouter
         {
             FeedbackCommandKind.PlasmaClear => target.Plasma!.ClearAsync(),
             FeedbackCommandKind.PlasmaRow => target.Plasma!.RowAsync(command.Y, command.Data!),
-            _ => target.Plasma!.PosTextAsync(command.Text ?? string.Empty, command.X, command.Y),
+            FeedbackCommandKind.PlasmaBox =>
+                target.Plasma!.BoxAsync(command.X, command.Y, command.Width, command.Height),
+            _ => target.Plasma!.PosTextAsync(command.Text ?? string.Empty, command.X, command.Y,
+                                             0, command.Font),
         };
 
         write.ContinueWith(w =>