chore: checkpoint web Blender migration source, tools and docs

Accumulated uncommitted work: GHOST Web backend, WebGL/GPU web layer,
web workflow engine and protocol, tooling, docs and task records.
Large generated evidence, user-testing archives, build snapshots and
imported test assets remain untracked.

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

blender-5.2.0/source/blender/blenkernel/intern/context.cc

@@ -44,6 +44,9 @@
 #include "RE_engine.h"
 
 #include "RNA_access.hh"
+#ifdef WITH_WEB
+#  include "RNA_access_guard.hh"
+#endif
 #include "RNA_prototypes.hh"
 #include "RNA_types.hh"
 
@@ -93,6 +96,7 @@ struct bContext {
   struct {
     Main *main;
     Scene *scene;
+    ViewLayer *view_layer;
 
     int recursion;
     /** True if python is initialized. */
@@ -130,9 +134,32 @@ bContext *CTX_copy(const bContext *C)
 
 void CTX_free(bContext *C)
 {
+#ifdef WITH_WEB
+  /* Poll-message cleanup can release Python callbacks. Suspended RNA accesses
+   * must stop before those callbacks re-enter with a context being destroyed. */
+  RNAMainAccessScope::context_destroyed(C);
+#  ifdef WITH_PYTHON
+  /* All native context owners pass here, not just the WebEngine wrapper.
+   * Poll-message finalizers must not obtain a context being retired via bpy. */
+  if (BPY_context_get() == C) {
+    BPY_context_set(nullptr);
+  }
+#  endif
+#endif
   /* This may contain a dynamically allocated message, free. */
   CTX_wm_operator_poll_msg_clear(C);
 
+#ifdef WITH_WEB
+  /* Also retire pending accesses created by the cleanup callback itself. */
+  RNAMainAccessScope::context_destroyed(C);
+#  ifdef WITH_PYTHON
+  /* A nested callback can have rebound the module while clearing the poll
+   * message. Never leave that slot pointing at the allocation freed below. */
+  if (BPY_context_get() == C) {
+    BPY_context_set(nullptr);
+  }
+#  endif
+#endif
   MEM_delete(C);
 }
 
@@ -1310,6 +1337,11 @@ Main *CTX_data_main(const bContext *C)
 
 void CTX_data_main_set(bContext *C, Main *bmain)
 {
+#ifdef WITH_WEB
+  if (C->data.main != bmain) {
+    RNAMainAccessScope::context_main_changed(C);
+  }
+#endif
   C->data.main = bmain;
   BKE_sound_refresh_callback_bmain(bmain);
 }
@@ -1353,6 +1385,14 @@ ViewLayer *CTX_data_view_layer(const bContext *C)
       return view_layer;
     }
   }
+  else if (scene && C->data.view_layer) {
+    /* RNA can remove a layer between calls. Compare membership before dereferencing. */
+    for (ViewLayer &candidate : scene->view_layers) {
+      if (&candidate == C->data.view_layer) {
+        return &candidate;
+      }
+    }
+  }
 
   return BKE_view_layer_default_view(scene);
 }
@@ -1531,6 +1571,9 @@ const char *CTX_data_mode_string(const bContext *C)
 
 void CTX_data_scene_set(bContext *C, Scene *scene)
 {
+  if (C->data.scene != scene) {
+    C->data.view_layer = nullptr;
+  }
   C->data.scene = scene;
 
 #ifdef WITH_PYTHON
@@ -1541,6 +1584,11 @@ void CTX_data_scene_set(bContext *C, Scene *scene)
 #endif
 }
 
+void CTX_data_view_layer_set(bContext *C, ViewLayer *view_layer)
+{
+  C->data.view_layer = view_layer;
+}
+
 ToolSettings *CTX_data_tool_settings(const bContext *C)
 {
   ToolSettings *toolsettings;