examples/war: redesign card art — opaque bodies, 16x16 pips, checkerboard back

The first-pass card tiles were riddled with palette-0 transparent
pixels that let the felt background bleed through every rank
glyph, small suit, and big pip. At arm's length the cards looked
like they had green specks eating them. This commit rewrites all
of the card art from scratch:

- **Opaque card bodies.** Every pixel inside a card tile is now
  either white (palette 2), red (1), or black (3). No `.` values
  anywhere on a face or back tile. The green felt only shows
  outside the card rectangle, where it should.

- **Readable rank glyphs.** The 13 rank tiles (A, 2-9, 10, J, Q, K)
  are now drawn as bold black strokes on a solid white body. The
  "holes" of the letters (e.g. the triangle inside an "A") are
  white, not transparent.

- **16x16 big pips.** The big centre pip is now a 4-tile (16x16)
  shape split into TL/TR/BL/BR quadrants per suit. Previously it
  was a 2-tile (16x8) half-height strip that looked cramped. The
  TL/TR quadrants kept their existing tile indices (28-35) so the
  shift is local; the new BL/BR quadrants are appended after the
  BIG WAR letters at tiles 88-95 to avoid renumbering the entire
  alphabet / digits / UI tile range.

- **Distinct suit shapes.** Spade is a smooth teardrop with a
  short stem and base; heart is two symmetric lobes with a V
  bottom; diamond is a clean rhombus; club is three circles
  joined over a stem. Side-by-side they are unmistakable.

- **Clean checkerboard card back.** The old card back was a
  diamond lattice that had the same transparent-bleed problem
  and looked noisy anyway. Replaced with a crisp 2-pixel black-
  and-white checkerboard that tiles seamlessly across the card
  back's 16x24 footprint.

- **draw_card_face now emits 6 sprites in a rank/suit + 4-tile
  big-pip layout.** The previous 6-sprite layout was
  `[rank][ssuit] / [pipL][pipR] / [blankL][blankR]`; the new
  one is `[rank][ssuit] / [pipTL][pipTR] / [pipBL][pipBR]` with
  the bottom row carrying the bottom half of the big pip
  instead of being wasted blank tiles.

Also:
- New constants TILE_PIP_TL_BASE / TR / BL / BR replace the old
  TILE_PIP_L_BASE / TILE_PIP_R_BASE in constants.ne.
- Refreshed war.nes and the goldens. Every emulator harness
  test still passes (31/31).

https://claude.ai/code/session_0143dTgh3UeRrtfHgQwzcv5z

examples/war/constants.ne

@@ -59,9 +59,16 @@ const TILE_RANK_BASE: u8 = 11      // 13 tiles: A, 2..10, J, Q, K
 // Small suit glyphs for the card corner, one per suit.
 const TILE_SUIT_SMALL_BASE: u8 = 24  // 4 tiles: ♠ ♥ ♦ ♣
 
-// Big centre-pip, authored as a 16×8 pair per suit (left half + right half).
-const TILE_PIP_L_BASE: u8 = 28       // 4 tiles
-const TILE_PIP_R_BASE: u8 = 32       // 4 tiles
+// Big centre-pip, authored as a 16×16 shape split into four 8×8
+// quadrants per suit. Each `_BASE + suit` picks the tile for that
+// suit's quadrant. The TL/TR quadrants are contiguous at 28-35;
+// the BL/BR quadrants live at 88-95 because they were added
+// after the alphabet / digit / BIG WAR tiles and putting them in
+// the middle would have shifted every later tile's index.
+const TILE_PIP_TL_BASE: u8 = 28      // spade/heart/diamond/club TL
+const TILE_PIP_TR_BASE: u8 = 32      // spade/heart/diamond/club TR
+const TILE_PIP_BL_BASE: u8 = 88      // spade/heart/diamond/club BL
+const TILE_PIP_BR_BASE: u8 = 92      // spade/heart/diamond/club BR
 
 // Alphanumerics (8×8) used for all on-screen text that lives on the
 // sprite layer. Letters A-Z then digits 0-9, contiguous.