Grant the default drop target only to a lone zone

app/MindWork AI Studio/Plugins/assistants/README.md

@@ -173,6 +173,7 @@ Launchers with an own icon or extra Lua code keep the plugin code editor and the
 - `WEB_CONTENT_READER`: renders `ReadWebContent`; include `Name`, `UserPrompt`, `Preselect`, `PreselectContentCleanerAgent`.
 - `FILE_CONTENT_READER`: renders `ReadFileContent`; use it when exactly one expected file should be read and inserted into the prompt; include `Name`, and optionally `UserPrompt`, `ShowAttachedDocumentState`, `Class`, `Style`. `ShowAttachedDocumentState` defaults to `true`; set it to `false` only when the loaded-document indicator should be hidden.
 - `FILE_ATTACHMENTS`: renders `AttachDocuments`; use it when the assistant should accept multiple documents/images or an unpredictable number of files as context; include `Name`, and may include `Heading`, `UserPrompt`, `CatchAllDocuments`, `UseSmallForm`, `Class`, `Style`. Keep `UseSmallForm = false` by default unless compact layout is explicitly required.
+- **Drop zones and `CatchAllDocuments`**: `FILE_CONTENT_READER` and `FILE_ATTACHMENTS` both accept dropped files. `CatchAllDocuments` makes one of them the default target of the whole assistant, so that a file dropped anywhere in it still arrives there. That only makes sense while the assistant has exactly **one** drop zone. With several, set `CatchAllDocuments = false`: it defaults to `true` when the prop is absent, and users then have to aim at the zone they mean instead of watching their file land in a neighbouring one. AI Studio enforces the rule at runtime, so a `true` value is ignored anyway as soon as a second drop zone exists.
 - `IMAGE`: embeds a static illustration; `Props` must include `Src` plus optionally `Alt` and `Caption`. `Src` can be an HTTP/HTTPS URL, a `data:` URI, or a plugin-relative path (`plugin://assets/your-image.png`). The runtime will convert plugin-relative paths into `data:` URLs (base64).
 - `HEADING`, `TEXT`, `LIST`: descriptive helpers.