Add custom ZebraFontD bitmap TrueType font to reduce Font D rendering diff

[Copilot]

Font D diffs (kmart, dpdpl, dhlparceluk) are driven by glyph shape mismatch — DejaVu Mono Bold's outlines don't resemble Zebra's built-in bitmap Font D characters at all. Replacing the backing font with one whose glyphs actually match Zebra's pixel patterns reduces this diff.

Changes

• scripts/generate_zebra_font_d.py — fonttools-based generator that encodes pixel-accurate 12×14–17 bitmaps (uppercase, digits, punctuation) as filled TrueType rectangles. Characters extracted pixel-by-pixel from Labelary reference images (testdata/kmart.png); remaining characters designed in the same style with accurate 2-pixel-wide strokes matching Zebra Font D. Font metrics are intentionally kept identical to DejaVu Mono Bold (UPM=2048, ascent=1901, descent=-483, h_advance=1233) so the existing 2.317 advance-width ratio calibration in font.rs requires no changes.

  Key generator fixes:

  • Corrected Y_SCALE: ab_glyph uses v_scale_factor = scale.y / height_unscaled where height_unscaled = ascent − descent = 2384, not UPM. The old formula rendered each bitmap row at 0.859 px instead of 1 px. Fixed to Y_SCALE = 2384 / (18 × 7/6) ≈ 113.52.
  • Accurate 2-pixel-wide stroke bitmaps for all uppercase letters and digits extracted from the kmart Labelary reference.
  • ( and ) extended to 17 rows to match the reference descender zone.

• src/assets/fonts/ZebraFontD.ttf — Regenerated font embedded as a static asset (~38 KB).

• src/assets/mod.rs — Exposes FONT_ZEBRA_D static byte slice.

• src/drawers/renderer.rs — Routes font name "D" to FONT_ZEBRA_D instead of DejaVu Mono Bold:

  "D" => FONT_ZEBRA_D,
  "B" | "P" | "Q" | "S" => FONT_DEJAVU_BOLD,

Diff impact

Label	Before	After
kmart	7.03%	6.93%
dpdpl	6.38%	6.08%
dhlparceluk	5.14%	4.82%

[GOODBOY008]

@copilot adjust the new font to enhance the diff report

[Copilot]

@copilot adjust the new font to enhance the diff report

Done in commit 507f81a. Two improvements were made:

1. Fixed Y_SCALE formula: ab_glyph uses v_scale_factor = scale.y / height_unscaled where height_unscaled = ascent − descent = 2384, not UPM. The old formula gave 0.859 px/row instead of 1 px — characters were rendering shorter and blurry at row boundaries. Fixed to Y_SCALE = 2384 / (18 × 7/6) ≈ 113.52.

2. Accurate 2-pixel-wide stroke bitmaps: Extracted all uppercase letters and digits pixel-by-pixel from the kmart Labelary reference. Zebra Font D uses 2-pixel-wide strokes throughout — H, N, L, P, T, I, E, C, D, G, O, R, S and the digits were all updated. ( and ) were extended to 17 rows to match the reference.

Label	Before	After
kmart	6.98%	6.93%
dpdpl	6.31%	6.08%
dhlparceluk	4.87%	4.82%