refactor(app): compose world rendering startup

Move Region/environment, mandatory modern rendering, terrain, WB, texture, and sampler construction behind the typed Phase-4 composition boundary. Give every fallible GL constructor prefix retryable ownership so partial startup failure cannot leak or replay resource deletion while preserving the accepted render path and DAT inputs.

Co-authored-by: Codex <codex@openai.com>

docs/architecture/code-structure.md

@@ -721,10 +721,17 @@ atomic update/render frame-root slot, and a prepare-aware portal fallback and
 transfer slot. GL construction and state mutations now use checked commit
 boundaries with exact retry ownership for failed names, bindless residency,
 and texture-binding restoration. `GameWindow` is 3,689 raw lines / 162 fields /
-37 methods. Checkpoints I–L remain active, with ordered production composition
-next. The Checkpoint H production App build is warning-free, its 61 focused
-ownership tests pass, the complete Release suite passes 7,606 tests / 5 skips,
-and all three final corrected-diff reviews are clean.
+37 methods at H. Checkpoint I.1–I.5 now provide the executable nine-phase
+oracle, platform/host/content/settings phases, and the production world/render
+phase. `WorldRenderCompositionPhase` owns Region/environment, the mandatory
+modern-renderer foundation, immutable terrain-worker inputs, and WB/texture/
+sampler construction; every Phase-4 GL constructor has retryable prefix
+ownership. `GameWindow` is 3,522 raw lines after I.5. Checkpoints I.6–L remain
+active, with retained UI and live presentation composition next. The current
+production App build is warning-free; the App gate passes 3,373 tests / 3
+intentional skips and the complete Release suite passes 7,745 tests / 5
+intentional skips. I.5's corrected-diff behavior, architecture, and
+adversarial reviews are clean.
 
 ### 4.4 Exit criteria