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/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