web: MODULARIZE build + embedded JS-integration example + selection callback

Restructure the web viewer so the wasm is a reusable module and add a
second example that drives it from ordinary page DOM.

Build:
- Emit IfcViewerWeb.js (a `createIfcViewer` factory, MODULARIZE) + .wasm
  instead of a single baked page (dropped --shell-file); copy the static
  example pages next to it at build time.
- Unbreak the web build: CameraMath.h / ViewportCore.cpp used
  boost::math::constants::pi just for pi, pulling all of boost/math into a
  header shared with the Emscripten build (no Boost in its sysroot). Replace
  with a constexpr kPiF — identical value, no dependency, desktop unaffected.

JS integration (web/ifcviewer.js):
- A small helper wraps the factory: boots the viewer on a canvas, runs the
  RAF loop from onRuntimeInitialized (NOT a post-await .then, which stalls
  Dawn-web's device callback and leaves the device half-initialised), and
  exposes addFile/addUrl, clearScene, model list/progress, and onSelect(...).
- ViewportCore/main_web emit each pick to JS via Module.__ifcvOnSelect
  (object id + IFC GlobalId + model index; empty on deselect); onSelect also
  dispatches an 'ifcviewer:select' DOM event.
- Fix input coords for a non-fullscreen canvas: mousemove/mouseup are
  window-targeted, so convert their coords to canvas-relative via the canvas
  client-rect origin (marquee + box-pick were offset when embedded).

Examples:
- IfcViewerWeb.html: the fullscreen viewer (same DOM/behaviour as before,
  now loading the module) — the Playwright smoke suite still targets it.
- embedded.html: a sized viewer with DOM outside it to add models (file or
  URL), list loaded models with streaming progress, and show the model +
  GlobalId of the clicked object. Starts empty (drops the wasm's embedded
  sample, which the fullscreen page/tests still use).
- index.html links both.

Federation note: the web viewer already streams multiple models into one
scene (a byte-source per file/URL); it doesn't need the desktop Federation
document for this. Verified: 11/11 web smoke tests pass; embedded example
loads models, reports the picked model + GUID, and the marquee aligns.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ifcviewer-web/CMakeLists.txt

@@ -89,26 +89,32 @@ target_link_options(IfcViewerWeb PRIVATE
     # also instrument every function reachable from emscripten_sleep,
     # adding ~30% to wasm size for no win here.
     #
-    # EXIT_RUNTIME=0 + Module.noExitRuntime=true (set in shell.html)
+    # EXIT_RUNTIME=0 + Module.noExitRuntime=true (set in the host page (web/ifcviewer.js))
     # keeps wasm alive after main() returns so Dawn-web's
     # RequestAdapter/RequestDevice promise callbacks land. The
     # alternative — calling emscripten_set_main_loop_arg early in
     # main() to set noExitRuntime as a side effect — registers a RAF
     # that starves the device promise (observed: ~10s delay in Firefox).
     "-sEXIT_RUNTIME=0"
+    # Emit a reusable module factory (IfcViewerWeb.js) instead of a baked page,
+    # so multiple static example pages can load the same wasm. Each page does
+    #   createIfcViewer({ canvas, ... }).then(Module => …)
+    # (see web/ifcviewer.js, which wraps this into a small integration API).
+    "-sMODULARIZE=1"
+    "-sEXPORT_NAME=createIfcViewer"
     # Expose the C entry points to JS. _raf_tick_c drives the RAF loop
-    # (shell.html); _load_sidecar_from_blob_c loads a user-picked File via
+    # (the host page (web/ifcviewer.js)); _load_sidecar_from_blob_c loads a user-picked File via
     # byte-range Blob.slice reads; _load_sidecar_from_url_c streams a remote
     # sidecar via HTTP Range; _ifcv_on_range_done / _ifcv_source_ready are the
     # JS→C completion callbacks for a landed range / a resolved URL size.
     # EMSCRIPTEN_KEEPALIVE alone keeps the symbols in the binary but doesn't
-    # add them to Module. ccall lets shell.html pass a JS string (the ?model
+    # add them to Module. ccall lets the host page (web/ifcviewer.js) pass a JS string (the ?model
     # URL) to load_sidecar_from_url_c without manual heap marshalling.
     "-sEXPORTED_FUNCTIONS=['_main','_raf_tick_c','_load_sidecar_from_source_c','_clear_scene_c','_ifcv_on_range_done','_ifcv_chunks_resident_c','_ifcv_chunks_total_c','_ifcv_model_count_c','_ifcv_model_resident_c','_ifcv_model_total_c','_ifcv_bytes_total_c','_ifcv_bytes_needed_c','_ifcv_bytes_loaded_c','_view_all_c','_frame_selection_c','_toggle_projection_c','_projection_is_ortho_c','_standard_view_c','_toggle_fly_c','_fly_is_active_c','_hide_selected_c','_isolate_selected_c','_show_all_c','_toggle_xray_c','_xray_is_active_c','_toggle_section_c','_clear_section_c','_section_is_active_c']"
-    # ccall: shell.html passes the ?model URL string to load_sidecar_from_url_c.
+    # ccall: the host page (web/ifcviewer.js) passes the ?model URL string to load_sidecar_from_url_c.
     # HEAPU8: lets tooling/tests read the wasm heap size (e.g. to verify a large
     # sidecar streams by range instead of loading whole). Standard, zero-cost.
-    "-sEXPORTED_RUNTIME_METHODS=['ccall','HEAPU8']"
+    "-sEXPORTED_RUNTIME_METHODS=['ccall','HEAPU8','UTF8ToString']"
     # Streaming + chunked geometry want a heap that can grow as buffers
     # arrive. 256 MB initial, 2 GB ceiling (matches the wasm32 pointer
     # cap; --shared64 / MEMORY64 would lift this later if we need it).
@@ -124,7 +130,22 @@ target_link_options(IfcViewerWeb PRIVATE
     # mounts the file at the virtual path the wasm fopen()s. User-picked
     # files instead stream via Blob.slice byte ranges (load_sidecar_from_blob_c).
     "--embed-file=${CMAKE_CURRENT_SOURCE_DIR}/sample.ifcview@/sample.ifcview"
-    # Shell template wraps the JS output in our canvas page.
-    "--shell-file=${CMAKE_CURRENT_SOURCE_DIR}/shell.html"
 )
-set_target_properties(IfcViewerWeb PROPERTIES SUFFIX ".html")
+# MODULARIZE emits IfcViewerWeb.js (the createIfcViewer factory) + .wasm.
+set_target_properties(IfcViewerWeb PROPERTIES SUFFIX ".js")
+
+# Copy the static example pages + the JS integration helper next to the wasm so
+# a plain `python3 -m http.server --directory build-web` serves the whole demo:
+#   /IfcViewerWeb.html  fullscreen example
+#   /embedded.html      embedded viewer + DOM model list / selection (JS API)
+#   /index.html         links to both
+set(IFCVIEWERWEB_STATIC
+    "${CMAKE_CURRENT_SOURCE_DIR}/web/ifcviewer.js"
+    "${CMAKE_CURRENT_SOURCE_DIR}/web/IfcViewerWeb.html"
+    "${CMAKE_CURRENT_SOURCE_DIR}/web/embedded.html"
+    "${CMAKE_CURRENT_SOURCE_DIR}/web/index.html"
+)
+add_custom_command(TARGET IfcViewerWeb POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E copy_if_different
+            ${IFCVIEWERWEB_STATIC} "$<TARGET_FILE_DIR:IfcViewerWeb>"
+    COMMENT "Copying web example pages next to IfcViewerWeb.js")