MCP: document.json checks brush art and relative link paths against the read roots

Under --automation-read-root, document.json names a linked image or
placed file in a stored brush's art outside the read roots by its file
name alone, as it does in the layers. A stored brush entry that does not
read as a brush is left out of the reply, and a stored brush library
that is not a list becomes an empty one. A link whose file is inside the
read roots loses its stored relative path when that path leads outside
them, from the folder of the file the document was read from or from the
document's own folder.

docs/mcp.md

@@ -172,9 +172,11 @@ the suite) keep the agent to the folders you give it:
   read roots, and the preset stays. The preferences themselves are not changed.
 - `document.inspect` (`inspect_document`) gives `path` as null when the document's file is outside the read roots.
   `document.json` names a linked image or placed file outside them by its file name alone in the link's `path`, and
-  leaves out the link's `relative`, `size` and `modified`. It also names a data set's image value outside them by
-  its file name alone, and leaves out the `folder` of `export_settings` (the settings Export for Screens last used)
-  when that folder is outside them. The document itself is not changed.
+  leaves out the link's `relative`, `size` and `modified`. This covers the art of the brushes in `unknown.brushes`
+  too. A link whose file is inside them keeps its `path` but leaves out a `relative` that leads outside them. A
+  stored brush entry that does not read as a brush is left out of `unknown.brushes`. `document.json` also names a data set's image
+  value outside them by its file name alone, and leaves out the `folder` of `export_settings` (the settings Export
+  for Screens last used) when that folder is outside them. The document itself is not changed.
 - Each flag may be given more than once (#3546): a path inside any of the read roots may be read, one inside any
   of the write roots written, so one session can read a project folder and a shared assets folder, or write to an
   output folder and a scratch folder, without widening a root to their common parent. A folder given twice

docs/target-app-parity.md

@@ -764,7 +764,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - Saves, Export for Screens and Package under `--automation-read-root`: a save without a path leaves the document's own file out of its reply, and a save without a path known leaves out the suggested folder, when they are outside the read roots; Export for Screens into an export preset's folder outside them lists its files relative to that folder and names that folder by its name in an error, and the export settings and saved presets leave out a folder outside them when read or exported; Package's report and warnings, and Document Info's linked images, name a file outside them by its file name. A path the client gives stays in the reply. `crates/engine/src/tests/save.rs`, `crates/engine/src/cmd/fileio/tests_screens.rs`, `crates/engine/src/tests/package.rs`, `crates/ui-egui/src/tests/automation.rs`.
   - `ui.inspect` under `--automation-read-root`: the documents still opening, the recent files, library panels' files and folder preferences (saved, and in an open Preferences dialog) outside the read roots are left out of the reply, a library loaded from outside them shows by its file name in `ui.inspect` and `ui.docking`, and the app's state is not changed. `crates/ui-egui/src/tests/automation.rs` (`ui_inspect_leaves_out_paths_outside_the_read_root`).
   - Link replies under `--automation-read-root`: `links.list`, `links.check`, `links.info` and `document.open`'s link rows leave out the path, found path and folder of a linked file outside the read roots, and the stored size and date of it in `links.info`; each row keeps its id, file name and status, and the document's links are not changed. `crates/engine/src/tests/linkspanel.rs` (`link_paths_outside_the_read_roots_are_left_out`), `crates/engine/src/tests/placed_document.rs` (`link_info_leaves_out_a_placed_documents_path_outside_the_read_roots`).
-  - Document replies under `--automation-read-root`: `document.inspect` gives `path` as null for a document file outside the read roots, and `document.json` names a linked image or placed file outside them by its file name alone, without its relative path, size or date, and a data set's image value outside them by its file name, and leaves an Export for Screens folder outside them out of `export_settings`; the document is not changed. `crates/engine/src/tests/placed_document.rs` (`document_replies_leave_out_paths_outside_the_read_roots`).
+  - Document replies under `--automation-read-root`: `document.inspect` gives `path` as null for a document file outside the read roots, and `document.json` names a linked image or placed file outside them by its file name alone, without its relative path, size or date, brush art included, leaves out a relative path that leads outside them and a stored brush entry that does not read as a brush, names a data set's image value outside them by its file name, and leaves an Export for Screens folder outside them out of `export_settings`; the document is not changed. `crates/engine/src/tests/placed_document.rs` (`document_replies_leave_out_paths_outside_the_read_roots`, `document_json_checks_brush_art_and_relative_paths_against_the_read_roots`).
   - Swatch, brush, symbol and graphic style library lists under `--automation-read-root`: library files and the user library folder outside the read roots are left out, a library loaded from outside them is listed and found by its file name, and the app's own list is not changed. `crates/engine/src/tests/library_roots.rs`.
   - Preferences commands under `--automation-read-root`: `prefs.get`, `prefs.list`, `prefs.set` and `prefs.reset` show folder preferences outside the read roots as `null` and leave out an export preset's folder outside them, and the preferences are not changed. `crates/engine/src/tests/prefs_roots.rs`.
   - Scripts: `alert`, `confirm` and `prompt` open dialogs during a run, each with a Stop button that ends the run and puts every document back. In the app the run waits at the call for the person's answer; a run over MCP or the command line takes its answers in order from `script.run`'s `answers`, and the report lists each dialog with its answer. `crates/engine/src/tests/script_dialogs.rs`, `crates/ui-egui/src/tests/script_dialogs.rs`.