Read roots: links.findFiles and image.info follow the configured read roots

With automation read roots in force, links.findFiles and text.findFontFiles
replies, including later polls and stops of a search another client started,
leave out the files found outside the caller's read roots, a sought link's
saved path outside them and the folder searched when it is outside them. A
failed search then gives its reason without the path. The rows keep their
names, ids and status, and the counts stay.

image.info gives link: null for a linked file outside the read roots, as
links.info does. text.addFontFiles gives folder: null when the Fonts folder
is outside the read roots and names the copies there by their file names;
the fonts are still copied.

Docs: docs/mcp.md, docs/target-app-parity.md.

docs/mcp.md

@@ -201,6 +201,14 @@ the suite) keep the agent to the folders you give it:
   and `modified` the document keeps of that file. Each row keeps its id, `name` (`fileName`), status and other
   fields. This applies to every document, also one the person or a client with wider roots opened. The paths a
   client gives `links.relink` and `links.unembed` stay in their replies, and the document's links are not changed.
+- `image.info` gives `link: null` for a linked file outside the read roots, as `links.info` leaves it out; its id,
+  name, `linked` and the other fields stay. `links.findFiles` and `text.findFontFiles` replies, including later
+  `{}` and `{stop: true}` calls on a search another client started, leave out the files found outside the read
+  roots (with their `size` and `match`), a sought link's `path` outside them, and `folder` when the folder searched
+  is outside them; `error` then gives the reason without the path (for example `the folder can't be read`). The
+  rows keep their `name`, `ids`, family, style and status, and the counts stay. `text.addFontFiles` gives
+  `folder: null` when VectorCraft's Fonts folder is outside the read roots, and only the file name in `copied` and
+  `kept` `to` and in `skipped` `file` for a path outside them; the fonts are still copied.
 - `prefs.get`, `prefs.list`, `prefs.set` and `prefs.reset` show a folder preference outside the read roots
   (`fontsFolder`, `pluginsFolder`, `scratchPrimary`, `scratchSecondary`, `recoveryFolder`, `templatesFolder`) as
   `null`; an empty folder and the scratch disk choices `Startup` and `None` stay. In `prefs.get {}` and