feat(stdlib): Tiled P6 — infinite/chunked maps, .world stitching, base64+zstd (#74)

- Infinite/chunked maps: <chunk x y width height> (TMX) and JSON chunks[]
  (default 16x16) decode and flatten into the dense layer array, sized to the
  chunk union; the map's 0/0 header dimensions fall back to the flattened bounds.
- .world stitching: Tiled.world / Tiled.world_count / Tiled.world_map read a
  .world (JSON, reusing Json.parse) and list its member maps at their offsets.
- base64+zstd: a self-contained pure-Ludic Zstandard decompressor
  (runtime/native/zstd.ludic, RFC 8878) — the design's "largest single item,
  explicitly last". Frame header + raw/RLE/compressed blocks; raw/RLE and
  direct-weight Huffman literals; the full FSE sequence path (predefined,
  transcribed exactly from zstd's hardcoded tables since they're not rebuildable
  from the default distributions; RLE; FSE-described) with repeat offsets and
  execution. Decodes the low-entropy GID streams a tilemap produces; a high-
  entropy FSE-compressed-Huffman-weights block fails cleanly with -1 rather than
  emitting wrong bytes (documented scope).

Proven by library/tiled_p6.ludic (12 assertions): TMX + TMJ chunk flattening,
.world offsets, and a real zstd-compressed tile layer decoding byte-exactly to
its CSV baseline. x test: 97 passed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/docgen/inventory.json

@@ -718,6 +718,9 @@
     "tiled-layer_opacity",
     "tiled-layer_tint",
     "tiled-layer_offsetx",
-    "tiled-layer_offsety"
+    "tiled-layer_offsety",
+    "tiled-world",
+    "tiled-world_count",
+    "tiled-world_map"
   ]
 }

tools/x/test.ludic

@@ -212,6 +212,7 @@ function cmd_test() -> int {
   feat_case("library/tiled_p3", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14", "tiled_p3.ludic (Tiled P3: animated tiles -> deterministic frame clock + tile objects w/ flips; beach_tileset 33 anims; issue #71)")
   feat_case("library/tiled_p4", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18", "tiled_p4.ludic (Tiled P4: object shapes/text + custom props/types + templates + opt-in spawn; issue #72)")
   feat_case("library/tiled_p5", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14", "tiled_p5.ludic (Tiled P5: image/group layers + iso/hex/staggered coords + Wang GID resolution; issue #73)")
+  feat_case("library/tiled_p6", "", "1 2 3 4 5 6 7 8 9 10 11 12", "tiled_p6.ludic (Tiled P6: infinite/chunked maps + .world stitching + base64+zstd decompression; issue #74)")
   feat_case("library/render", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18", "render.ludic (Screen pixel/oval/camera/clip/blend_mode/measure_text + Camera set/follow/shake, verified by pixel readback)")
   feat_case("library/lighting", "", "1 2 3 4 5 6 7 8 9 10 11 12 13 14", "lighting.ludic (Light ambient/point radial falloff + occluder hard shadows — 2D light accumulation, verified by pixel readback)")
   feat_case("library/light_tiers", "", "1 1 1 1 1 1 1 1 1", "light_tiers.ludic (Light spot/falloff/soft/gel/normal/time_of_day — render-quality tiers 3-4; issue #49)")