Add claude docs

.claude/display-texture.md

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+# Display -- Texture, Tileset, and Font
+
+Source: `src/dusk/display/`
+
+See also: `.claude/display-core.md`, `.claude/display-shader.md`
+
+---
+
+## Texture (`texture.h`)
+
+```c
+extern texture_t TEXTURE_WHITE;  // 4x4 opaque white; always available
+
+errorret_t textureInit(
+  texture_t *texture,
+  int32_t width,
+  int32_t height,
+  textureformat_t format,
+  texturedata_t data
+);
+errorret_t textureDispose(texture_t *texture);
+```
+
+`textureformat_t` and `texture_t` are platform aliases
+(`textureformatplatform_t`, `textureplatform_t`). On OpenGL targets
+the format maps to GL texture format constants.
+
+`texturedata_t` is a union:
+- `.paletted.indices` + `.paletted.palette` -- for paletted formats
+- `.rgbaColors` -- for RGBA formats
+
+### Texture rules
+
+- Dimensions must be powers of two on PSP and GameCube/Wii. Use
+  `mathNextPowTwo` from `util/math.h` if needed.
+- Texture upload must happen on the main thread. In the asset loader,
+  this means `loadSync` (not `loadAsync`).
+- `TEXTURE_WHITE` is always available without loading; use it as a
+  placeholder or for untextured geometry.
+
+---
+
+## Tileset (`tileset.h`)
+
+A tileset subdivides a texture into a uniform grid of tiles.
+
+```c
+typedef struct {
+  uint16_t tileWidth, tileHeight;
+  uint16_t tileCount;
+  uint16_t columns, rows;
+  vec2 uv;   // UV size per tile (pre-computed from grid dimensions)
+} tileset_t;
+
+// Get UV rect for a tile by index:
+void tilesetTileGetUV(
+  const tileset_t *ts, uint16_t tileIndex, vec4 outUV
+);
+
+// Get UV rect for a tile by grid position:
+void tilesetPositionGetUV(
+  const tileset_t *ts, uint16_t column, uint16_t row, vec4 outUV
+);
+```
+
+`outUV` is `{u, v, u2, v2}` in normalised [0, 1] texture space.
+
+Tilesets are loaded from `.dtf` binary files via
+`ASSET_LOADER_TYPE_TILESET`. The DTF format stores tile width/height,
+grid dimensions, and per-tile UV offsets (magic + version header).
+
+---
+
+## Font (`font.h`)
+
+```c
+typedef struct {
+  texture_t *texture;
+  tileset_t *tileset;
+} font_t;
+```
+
+A font is a tileset-backed texture atlas where each tile is a character
+glyph. No heap allocation -- both pointers are owned by the caller.
+Character lookup is by glyph index into the tileset grid. Rendering is
+handled by the spritebatch system using the tileset UV helpers.