Export: warnings name an option the chosen format doesn't read

`document.export`, `document.serialize` and `document.exportSelection`
accept a key that only another format takes. `{"format": "pdf",
"quality": 80}` wrote the PDF and gave no warning about `quality`.

The reply's `warnings` now name each such key, in the wording of a
save's note: "`quality` was not used: PDF files don't read it".

- The format's own options, the commands' own keys, null values and an
  exporter plug-in's format get no note.
- The note names the kind of file written. A legacy `.ai` file
  (`aiVersion: "7"`) reads `outlineText`, `hiddenObjects`,
  `transparentImages`, the artboard choice and `useArtboards`, and
  beside `aiVersion` no other option. The other `.ai` files don't read
  those three options or `preserveEditing`, which is always on for
  them.
- An export doesn't read `separateArtboards`, or `range` for a
  `vectorcraft` or `template` file. A save reads them to write each
  artboard to a file of its own.
- In the app, an export that automation asked for (`app.export` with a
  path, `file.exportAs` run as a command) gives the same notes in its
  reply and in the status bar. A Background Export replies before the
  file is written, and that reply has the notes. An export that a
  person starts from the File menu gets none.
- Export As gives a template export no `useArtboards` or `range`: a
  template doesn't read them.
- `vectorcraft-cli convert` sends `outlineText` only with
  `--outline-text`, and `hiddenLayers` only to the formats that read
  it. A conversion then warns only about an option the command line
  gave.

`document.save` gives its notes as before: it does not apply the `.ai`
rules above.

Docs: docs/mcp.md, docs/control-protocol.md,
docs/target-app-parity.md, the params text of the three commands.

apps/vectorcraft-cli/src/main.rs

@@ -418,10 +418,18 @@ fn convert(args: &[String]) -> Result<(), String> {
         // Save as Template writes every artboard, with the .ai options.
         ("file.saveAsTemplate", json!({"path": output, "format": "ait", "outlineText": outline_text, "acknowledgeLoss": replace_lossy}))
     } else {
-        // A conversion keeps hidden layers and objects, written hidden, where the format can (SVG,
-        // PSD).
-        let params = json!({"path": output, "artboard": artboard, "range": range, "outlineText": outline_text, "hiddenLayers": true, "acknowledgeLoss": replace_lossy});
+        let params = json!({"path": output, "artboard": artboard, "range": range, "acknowledgeLoss": replace_lossy});
         let mut params = with_pixel_scale(params, &output, scale, ppi);
+        // An option the format doesn't read comes back in the warnings, so each goes out only
+        // when it was asked for: `outlineText` with --outline-text, and `hiddenLayers` to the
+        // formats that have it (SVG, PSD), where a conversion keeps hidden layers and objects,
+        // written hidden.
+        if outline_text {
+            params["outlineText"] = json!(true);
+        }
+        if vectorcraft_engine::cmd::fileio::writable_format(None, Some(&output)).is_ok_and(|f| f.options.iter().any(|o| o.name == "hiddenLayers")) {
+            params["hiddenLayers"] = json!(true);
+        }
         if let Some(decimals) = decimals {
             params["decimals"] = json!(decimals);
         }