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/windowmanager/WM_api.hh

@@ -36,6 +36,13 @@ class GHOST_IContext;
 
 namespace blender {
 
+#ifdef WITH_WEB
+/* Completed native saves and file-selector exports consumed by the browser GPU frame. */
+void WM_web_publish_save(const char *filepath, bool save_copy, bool save_as);
+std::optional<std::string> WM_web_take_export_path(std::optional<bool> *r_save_copy = nullptr,
+                                                bool *r_save_as = nullptr);
+#endif
+
 struct ARegion;
 struct GPUViewport;
 struct ID;
@@ -278,8 +285,12 @@ bool WM_desktop_cursor_sample_read(float r_col[3]);
 uint8_t *WM_window_pixels_read_from_frontbuffer(const wmWindowManager *wm,
                                                 const wmWindow *win,
                                                 int r_size[2]);
-/** A version of #WM_window_pixels_read_from_frontbuffer that samples a pixel at `pos`. */
-void WM_window_pixels_read_sample_from_frontbuffer(const wmWindowManager *wm,
+/** A version of #WM_window_pixels_read_from_frontbuffer that samples a pixel at `pos`.
+ *
+ * Returns false when the native front-buffer cannot be read, allowing browser callers to
+ * fall back to the slower off-screen compositor without publishing a false black sample.
+ */
+bool WM_window_pixels_read_sample_from_frontbuffer(const wmWindowManager *wm,
                                                    const wmWindow *win,
                                                    const int pos[2],
                                                    float r_col[3]);
@@ -388,6 +399,16 @@ void WM_window_set_active_screen(wmWindow *win, WorkSpace *workspace, bScreen *s
 ViewLayer *WM_window_get_active_view_layer(const wmWindow *win)
     ATTR_NONNULL(1) ATTR_WARN_UNUSED_RESULT;
 void WM_window_set_active_view_layer(wmWindow *win, ViewLayer *view_layer) ATTR_NONNULL(1);
+#ifdef __EMSCRIPTEN__
+/** Preflight the browser window family before replacing its view layer. A null
+ * target denotes a layer that is about to be created or removed. No mutation. */
+bool WM_window_web_view_layer_change_allowed(const wmWindowManager *wm,
+                                             const wmWindow *win,
+                                             const ViewLayer *view_layer,
+                                             ReportList *reports);
+/** Invalidate queued input before callbacks can consume the replacement layer. */
+void WM_window_web_view_layer_changed(wmWindow *win);
+#endif
 void WM_window_ensure_active_view_layer(wmWindow *win) ATTR_NONNULL(1);
 
 bool WM_window_is_temp_screen(const wmWindow *win) ATTR_WARN_UNUSED_RESULT;
@@ -506,6 +527,7 @@ bool WM_file_read(bContext *C,
                   const bool use_scripts_autoexec_check,
                   ReportList *reports);
 void WM_file_autosave_init(wmWindowManager *wm);
+bool WM_file_write_last_session(bContext *C, ReportList *reports);
 bool WM_file_recover_last_session(bContext *C,
                                   const bool use_scripts_autoexec_check,
                                   ReportList *reports);
@@ -1497,6 +1519,10 @@ void WM_operator_type_modal_from_exec_for_object_edit_coords(wmOperatorType *ot)
 void WM_uilisttype_init();
 uiListType *WM_uilisttype_find(StringRef idname, bool quiet);
 bool WM_uilisttype_add(uiListType *ult);
+/**
+ * Clear list type references without deleting saved list settings, then remove the type.
+ * With WITH_WEB, `bmain` may be null only when session teardown has no surviving owner Main.
+ */
 void WM_uilisttype_remove_ptr(Main *bmain, uiListType *ult);
 void WM_uilisttype_free();