Served with isolation headers; start-screen capability notices; tests on the real GPU (t88 phase 1)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/agent-log.md

@@ -4,6 +4,19 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-27: t88 phase 1, serving and capability checks (Claude Code + Codex)
+
+- The game must be served with COOP/COEP (README has nginx and Caddy lines; opening from disk is
+  dropped). The title screen checks `crossOriginIsolated` and a WebGPU adapter (`CAPS`,
+  `checkCapabilities` in `src/ui/title.js`) and shows a notice; warnings only until
+  `REQUIRE_GPU_AND_THREADS` is flipped in Phases 2-3.
+- Browser tests and tools load through `tools/browser.py` + `tools/server.py`, on the real GPU by
+  default (`--gpu soft` / `DEEPGRAIN_GPU=soft` for SwiftShader). `tools/caps.py` prints isolation
+  and WebGPU per browser; `test/firefox_smoke.py` runs in `run_all.py --browser` when Firefox is
+  installed. Chromium 156: isolated, WebGPU on the RTX 5070. Playwright Firefox 157: isolated, no
+  WebGPU (Linux).
+- Tests: `python3 test/run_all.py --browser` all passed on the real GPU.
+
 ## 2026-10-27: t88 phase 0, profiler and baseline (Claude Code + Codex)
 
 - `tools/perf.py` rewritten: real GPU (ANGLE Vulkan flags), served by the new `tools/server.py`