[Refactor] (MG_Config, MG_Backend/DirectVulkan, trace-replay): centralize Magma env parsing and rename R11G11B10F fallback

tools/trace_replay/run_macos_window_retrace_local.py

@@ -363,7 +363,7 @@ def run_case(case, backend, replay_exe, mobilegl_library, vulkan_icd):
     ]
     env = os.environ.copy()
     env["MOBILEGL_BACKEND_TYPE"] = backend
-    env["MOBILEGL_VULKAN_R11G11B10F_FALLBACK"] = "1"
+    env["MOBILEGL_MAGMA_R11G11B10F_FALLBACK"] = "1"
     if vulkan_icd:
         env["VK_ICD_FILENAMES"] = vulkan_icd
 

tools/trace_replay/skills/trace-fixture-authoring.md

@@ -376,7 +376,7 @@ or the install fails with `INSTALL_FAILED_UPDATE_INCOMPATIBLE`.
 
 Match the CI environment (`.github/workflows/apk.yml` matrix): the emulator
 boots with `--gpu software` + `MOBILEGL_RETRACE_USE_ANGLE=1` for `DirectGLES`
-and `--gpu lavapipe` + `MOBILEGL_VULKAN_R11G11B10F_FALLBACK=1` for
+and `--gpu lavapipe` + `MOBILEGL_MAGMA_R11G11B10F_FALLBACK=1` for
 `DirectVulkan`. The emulator's ANGLE-on-Vulkan GLES stack exercises genuinely
 different driver semantics than physical devices (e.g. indirect-draw
 `gl_InstanceID` handling), so treat AVD-only image mismatches as real signal,