Add audio variants to user input protocols (#33923)

## What changed

- Add remote and local audio variants to core and app-server user inputs, including generated JSON and TypeScript schemas.
- Preserve audio fields when converting app-server inputs and response content into thread items.
- Keep unsupported audio out of model requests, TUI rendering, text extraction, and truncated tool output, using explicit text placeholders where audio is submitted as a model input.

## Testing

- Cover app-server media conversion, unsupported-input placeholders, TUI omission, and tool-output truncation.

GitOrigin-RevId: 16152bf3af674575ce569764a8b472e032e7569d

codex-rs/ext/skills/src/selection.rs

@@ -36,7 +36,11 @@ pub(crate) fn collect_explicit_skill_mentions(
                 blocked_plain_names.insert(name.clone());
                 select_by_path(catalog, path, &mut seen, &mut selected);
             }
-            UserInput::Text { .. } | UserInput::Image { .. } | UserInput::LocalImage { .. } => {}
+            UserInput::Text { .. }
+            | UserInput::Image { .. }
+            | UserInput::LocalImage { .. }
+            | UserInput::Audio { .. }
+            | UserInput::LocalAudio { .. } => {}
             UserInput::Mention { .. } => {}
             _ => {}
         }