restore semantic bold rendering in terminal panes (T-73)

Bold attributes from terminal escapes now render in a real bold
weight instead of being silently flattened.

- pubspec.yaml: register JetBrainsMono Bold + BoldItalic at
  weight 700 under family JetBrainsMono. Files already shipped on
  disk; only the registration was missing.
- assets/licenses.yaml: bump JetBrainsMono weights_bundled to
  [Regular, Italic, Bold, BoldItalic] per D-42 (the entry must
  match what is actually wired into the family).
- lib/src/terminal/src/ui/painter.dart: revert the `bold: false`
  override and drop the workaround comment. Bold now flows from
  CellFlags.bold to TextStyle.fontWeight.
- test/terminal/painter_bold_metrics_test.dart: load Regular and
  Bold via FontLoader and assert paragraph maxIntrinsicWidth is
  identical (cell-grid drift = 0). JetBrainsMono Bold's monospace
  by spec; this test is the canary for the day someone swaps the
  font.
- test/goldens/goldens/{ci,linux}/clide_button.png: regenerate.
  ClideButton's label renders slightly heavier on the bold variant
  (expected — 0.28% pixel diff before regen).

Earlier perception of over-bolding in the Claude pane was
synthetic-bold smearing (Flutter overpaints when no Bold.ttf is
registered for the family), not legitimate bold rendering. Visual
A/B confirms a real Bold face renders crisp emphasis without the
smear, so no per-pane renderer config is needed.

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

lib/src/terminal/src/ui/painter.dart

@@ -126,8 +126,7 @@ class TerminalPainter {
 
   @pragma('vm:prefer-inline')
   void paintHighlight(Canvas canvas, Offset offset, int length, Color color) {
-    final endOffset =
-        offset.translate(length * _cellSize.width, _cellSize.height);
+    final endOffset = offset.translate(length * _cellSize.width, _cellSize.height);
 
     final paint = Paint()
       ..color = color
@@ -182,20 +181,15 @@ class TerminalPainter {
     if (paragraph == null) {
       final cellFlags = cellData.flags;
 
-      var color = cellFlags & CellFlags.inverse == 0
-          ? resolveForegroundColor(cellData.foreground)
-          : resolveBackgroundColor(cellData.background);
+      var color = cellFlags & CellFlags.inverse == 0 ? resolveForegroundColor(cellData.foreground) : resolveBackgroundColor(cellData.background);
 
       if (cellData.flags & CellFlags.faint != 0) {
         color = color.withOpacity(0.5);
       }
 
-      // Skip bold rendering — Flutter's synthetic bold (no Bold.ttf
-      // registered) drifts glyph advance widths slightly, breaking
-      // the cell grid. Color is enough to convey emphasis in TUIs.
       final style = _textStyle.toTextStyle(
         color: color,
-        bold: false,
+        bold: cellFlags & CellFlags.bold != 0,
         italic: cellFlags & CellFlags.italic != 0,
         underline: cellFlags & CellFlags.underline != 0,
       );