Register Composer 2.5 × Grok Build TUI; fix its MythiCraft enter-world crash

New Agent composer-2-5-grok-build (Composer 2.5 model in the Grok Build TUI
harness, contributor Nagi-ovo), two runs: mythos-craft + pelican-cycling.

mythos-craft fix (1 line): the WOOD block defines only top+side faces (no
bottom), but the atlas builder requests top/side/bottom for every block.
Fetching WOOD's bottom read t.bottom.image off undefined and threw a
TypeError at the top level of initTextures(), aborting init before the
"enter world" click listener attached — so clicking the start button did
nothing. getFaceImage now falls back to an existing face when one is
missing (bottom→top, the correct ring end-grain for a log). Verified in
headless Chrome: click now fires requestPointerLock and the overlay hides.

Artifacts renamed to the case-id convention; README registry rows synced
(Composer 2.5 now 3 runs across Cursor + Grok Build TUI).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.en.md

@@ -31,7 +31,7 @@ One-shot LLM eval cases by NAGI STUDIO: same prompt, different model x harness x
 | Gemini 3.1 Pro | Google | AntiGravity · High<br>Google AI Studio · High | 03 |
 | Gemini 3.5 Flash | Google | AntiGravity · High<br>Google AI Studio · High | 03 |
 | Grok Build | xAI | Grok Build TUI · Max | 02 |
-| Composer 2.5 | Cursor | Cursor · Max | 01 |
+| Composer 2.5 | Cursor | Cursor · Max<br>Grok Build TUI | 03 |
 | DeepSeek-V4-Pro | DeepSeek | Claude Code · Max | 02 |
 | Doubao Seed 2.0 Pro | ByteDance | Doubao Web · Pro Mode | 01 |
 | Doubao Seed 2.0 Mini | ByteDance | Doubao Web · Fast Mode | 01 |