Refactor documentation structure and add new specifications

- Updated MSH documentation to reflect changes in material, wear, and texture specifications.
- Introduced new `render.md` file detailing the render pipeline process.
- Removed outdated sections from `runtime-pipeline.md` and redirected to `render.md`.
- Added detailed specifications for `Texm` texture format and `WEAR` wear table.
- Updated navigation in `mkdocs.yml` to align with new documentation structure.

crates/texm/README.md

@@ -0,0 +1,15 @@
+# texm
+
+Парсер формата текстур `Texm`.
+
+Покрывает:
+
+- header (`width/height/mipCount/flags/format`);
+- core size расчёт;
+- optional `Page` chunk;
+- строгую валидацию layout.
+
+Тесты:
+
+- прогон по реальным `Texm` из `testdata`;
+- синтетические edge-cases (indexed + page, minimal rgba).