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
 

docs/plans/2026-07-22-gamewindow-slice-8-checkpoint-i-ordered-composition.md

@@ -253,6 +253,27 @@ Small implementation commits may be used while the checkpoint is active, but
 each must build and preserve production startup. The final I commit closes the
 ledger only after the complete pipeline is live.
 
+### Current implementation progress — 2026-07-22
+
+- I.1–I.4 are committed: the executable pipeline/rollback oracle, platform
+  acquisition, host input/camera, content/effects/audio, and settings/devtools
+  phases are the production startup path.
+- I.5 is complete. `WorldRenderCompositionPhase` now owns the ordered Region,
+  environment, mandatory bindless, terrain-atlas, shader, lighting, debug/HUD,
+  terrain, WB, texture, and sampler foundation. `GameWindow` is a write-only
+  publisher for this phase and no longer contains the Phase-4 construction
+  body.
+- Every fallible GL constructor in the Phase-4 prefix now publishes each name
+  into retryable construction ownership before later GL work. Failure testing
+  covers every composition boundary, every disposable publication, partial HUD
+  construction, reverse cleanup, retry, and no replay.
+- The I.5 tree is 3,522 raw `GameWindow.cs` lines. The App gate passes 3,373
+  tests / 3 intentional skips; the complete Release suite passes 7,745 tests /
+  5 intentional skips. Production App builds with zero warnings/errors; the
+  solution retains only the 17 warnings tracked by #228.
+- I.6 (retained UI plus live-presentation composition) is next. Checkpoint I
+  remains active until I.9 closes the complete nine-phase pipeline.
+
 ## 6. Automated acceptance
 
 ### Platform and pipeline