Actions: Batch keeps files named after data sets inside the destination folder

Batch over data sets names each output file after the document and the
data set, as the reference app's File + Data Set Name option does. It
joined that name onto the destination folder as it was, and a data set
name can hold any character. A data set named a/b failed to save, and
one named a/../../x wrote its file outside the destination folder. On
Windows, one named c\d also failed to save, and one named e:f left an
empty file.

The data set's name now goes through file_part, which Export for
Screens uses for its file name prefix and a format row's suffix, so
output file names have - in place of /, \ and : from a data set's name.
When two data sets then give the same name, compared without case, the
later ones get -2, -3 and so on, as artboard file names do, through a
distinct_names helper split out of unique_file_names. This covers the
folder destination and Override Save/Export.

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

docs/mcp.md

@@ -1927,7 +1927,10 @@ earlier step deleted the active artboard when it was the last one), the step get
 remote mode, MCP's `run_command` calls and each step of the `command_batch` tool get the active artboard too. The
 Actions panel plays an action as a `command.batch`. The Actions panel menu's Batch… runs
 `action.batch`: the same steps on every readable file in a folder (or every data set of the open document), with
-destination `none` | `saveAndClose` | `folder` and Override Open / Save / Export. Caps: 500 files or data sets, 8
+destination `none` | `saveAndClose` | `folder` and Override Open / Save / Export. Over data sets, the folder
+destination and the overrides name each file after the document and the data set (`<document>_<data set>.<ext>`).
+Batch writes `/`, `\` and `:` in the data set's name as `-`, and adds `-2`, `-3`… to a name an earlier data set
+used (compared without case). Caps: 500 files or data sets, 8
 folder levels, 256 steps. An action recorded in the Actions panel leaves the artboard out,
 and its steps of these commands get the artboard that is active when the action plays. A press with the Selection,
 Direct Selection or Group Selection tool inside an artboard makes that artboard the active one; with the Selection

docs/target-app-parity.md

@@ -414,6 +414,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - Variables: Update Data Set writes what the art holds into the active data set for the variables that data set holds, and keeps the data set's value for a variable whose objects are locked or inside a hidden or locked layer or group; `dataset.update {all: true}` also adds the other variables that the art reports a value for.
   - Variables: `dataset.select`, `dataset.next` and `dataset.prev` name the area type and type on a path whose text they rewrote and that doesn't fit, in the reply's `overflow` key, as `text.setText` does.
   - Actions panel (record/playback, persisted), generic parameter dialogs for every "…" command.
+  - Batch… over data sets names each file after the document and the data set (`action.batch`). It writes `/`, `\` and `:` in the data set's name as `-`, and adds `-2`, `-3`… to a name an earlier data set used.
   - Variables (data merge): text, visibility and image variables bound to objects (an object may carry several), dataset rows applied in one undo step (`variable.*`, `dataset.*`) from a Variables panel and Window › Variables, with dialogs to define, bind and edit, Make Text/Visibility/Image Dynamic, Capture/Update Data Set, CSV import/export (`dataset.import` / `dataset.export`), and a row in italics when an edit leaves the art not matching it; an image dataset value is a file path and apply keeps the object's bounds; bindings let go of deleted art and locked art is left alone; every command, like the rest, is drivable over MCP and the CLI.
   - Variables: Import Data Sets… (`dataset.import`) reads tab-separated files as well as comma-separated ones, and files without a `name` column, whose rows take the first free names Data Set 1, Data Set 2 and so on. An import error about a row's values or name gives the file line the row starts on.
   - JSON-lines control channel with real egui pointer and keyboard injection.