fix(web): review-round attachment refinements

Body-portal the lightbox and toast so transformed ancestors cannot trap
their fixed positioning (a lightbox opened from a chat message covered only
the chat column); make the toast pointer-transparent; observe the rail
element's own size instead of window resizes; consume vertical wheel ticks
exclusively via a non-passive listener with LINE/PAGE delta normalization;
keep the start position when the rail mounts over an existing draft; honor
prefers-reduced-motion for the toast, remove-control, and paging; retry
loads through the guarded load effect; note the deliberate promptError
re-announce; pin the intake toast in the assembled snapshot; sync the
superseded multimodal note and package docs.

pnpm-lock.yaml

@@ -1951,6 +1951,9 @@ importers:
       react:
         specifier: ^18.2.0
         version: 18.3.1
+      react-dom:
+        specifier: ^18.2.0
+        version: 18.3.1(react@18.3.1)
     devDependencies:
       '@deepseek-ai/cordis':
         specifier: workspace:^
@@ -1961,6 +1964,9 @@ importers:
       '@types/react':
         specifier: ~18.3.1
         version: 18.3.31
+      '@types/react-dom':
+        specifier: ~18.3.0
+        version: 18.3.7(@types/react@18.3.31)
 
   packages/client/ui-command:
     dependencies: