feat: add candidate FreeCAD naming SDK and attachment oracles

Build and verify the candidate-only FreeCAD naming bridge and OCCT worker path, including three-stage StringHasher restoration. Add Datum, ShapeBinder, attachment-mode, and PartDesign structure oracles plus offline SDK build plans and CI boundary checks.

native/freecad-naming-bridge/pre.js

@@ -0,0 +1,26 @@
+Module.preRun = Module.preRun || [];
+Module.preRun.push(() => {
+  for (const path of [
+    '/freecad-user',
+    '/freecad-user/config',
+    '/freecad-user/data',
+    '/freecad-user/cache',
+    '/freecad-user/temp',
+  ]) {
+    try {
+      FS.mkdir(path)
+    } catch (error) {
+      if (!FS.analyzePath(path).exists) throw error
+    }
+  }
+  Object.assign(ENV, {
+    HOME: '/freecad-user',
+    FREECAD_USER_HOME: '/freecad-user',
+    FREECAD_USER_DATA: '/freecad-user/data',
+    FREECAD_USER_TEMP: '/freecad-user/temp',
+    XDG_CONFIG_HOME: '/freecad-user/config',
+    XDG_DATA_HOME: '/freecad-user/data',
+    XDG_CACHE_HOME: '/freecad-user/cache',
+    TMPDIR: '/freecad-user/temp',
+  })
+})