Merge PR #4414: make terminal splash opaque

Co-authored-by: npub1mprnacetjua2xx3p5eddmhxyk6wv929ymm5py8kd2xfxurxahspqqlgyta <d8473ee32b973aa31a21a65adddcc4b69cc2a8a4dee8121ecd51926e0cddbc02@buzz.block.builderlab.xyz>
Signed-off-by: npub1mprnacetjua2xx3p5eddmhxyk6wv929ymm5py8kd2xfxurxahspqqlgyta <d8473ee32b973aa31a21a65adddcc4b69cc2a8a4dee8121ecd51926e0cddbc02@buzz.block.builderlab.xyz>

desktop/src/features/terminal/terminalBannerPainter.test.mjs

@@ -33,11 +33,15 @@ function canvas() {
   const draws = [];
   const clears = [];
   const colors = [];
+  const fills = [];
   const context = {
     _fillStyle: "",
     clearRect(...args) {
       clears.push(args);
     },
+    fillRect(...args) {
+      fills.push({ args, color: this._fillStyle, glyphsBefore: draws.length });
+    },
     fillText(...args) {
       draws.push(args);
       colors.push(this._fillStyle);
@@ -62,6 +66,7 @@ function canvas() {
     clears,
     colors,
     draws,
+    fills,
   };
 }
 
@@ -80,6 +85,19 @@ test("paints every emitted banner glyph at terminal cell coordinates", () => {
   assert.deepEqual(target.clears, [[0, 0, 1000, 600]]);
 });
 
+test("lays an opaque theme background under the banner before any glyph", () => {
+  const banner = buildTerminalBanner(112, 46, 17 / 8.4);
+  assert.ok(banner);
+  const target = canvas();
+  assert.equal(paintTerminalBanner(target.canvas, banner, palette, 2), true);
+  assert.equal(target.fills.length, 1);
+  const [ground] = target.fills;
+  assert.deepEqual(ground.args, [0, 0, 1000, 600]);
+  assert.equal(ground.color, palette.background);
+  assert.equal(ground.glyphsBefore, 0);
+  assert.ok(target.draws.length > 0);
+});
+
 test("uses visibly distinct theme-derived colors across banner layers", () => {
   const banner = buildTerminalBanner(112, 46, 17 / 8.4);
   assert.ok(banner);

desktop/src/features/terminal/terminalBannerPainter.ts

@@ -19,6 +19,11 @@ export function paintTerminalBanner(
   if (!context) return false;
   context.setTransform(dpr, 0, 0, dpr, 0, 0);
   context.clearRect(0, 0, bounds.width, bounds.height);
+  // The overlay sits above the grid canvas, so it needs its own opaque
+  // ground: without one the shell output painted underneath shows through
+  // the gaps between banner glyphs.
+  context.fillStyle = palette.background;
+  context.fillRect(0, 0, bounds.width, bounds.height);
   context.font = TERMINAL_CELL_METRICS.font;
   context.textBaseline = "alphabetic";