Variables: a data set with no value for any bound variable shows a status message

Choosing a data set in the Variables panel, stepping through data sets
with the panel's arrows, and running `dataset.select`, `dataset.next`
and `dataset.prev` applied nothing and showed no message when no object
was bound to a variable that the data set has a value for. This
happens, for example, after Import Data Sets… defines new variables
without binding them.

The app now shows "nothing in data set A was applied: no object is
bound to a variable it has a value for" in the status bar, and the three
commands add it to the reply as `warning`. A data set with a value for
a bound variable gives no warning even when every object bound to it is
locked; `skipped` counts those objects. What applying a data set does
is unchanged.

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

docs/mcp.md

@@ -1254,6 +1254,12 @@ defined. Of two variables of the same kind on one object, the one defined last w
 {"name":"run_command","arguments":{"command":"command.batch","params":{"label":"Offset","commands":[{"command":"object.move","params":{"dx":10,"dy":10,"copy":true}}]}}}
 ```
 
+When no object is bound to a variable that the data set has a value for, for example after `dataset.import` defines
+new variables without binding them, `dataset.select`, `dataset.next` and `dataset.prev` apply nothing and add
+`warning`, which the app's status bar shows: "nothing in data set A was applied: no object is bound to a variable it
+has a value for". A data set with a value for a bound variable gives no warning even when every object bound to it is
+locked; `skipped` counts those objects.
+
 `dataset.update {all?}` writes what the bound objects hold now into the active data set, for each variable that the
 data set holds. A variable whose objects report no value, because they are locked, inside a locked layer or group,
 or deleted, keeps the data set's value. With `all: true` it also adds every other variable that the

docs/target-app-parity.md

@@ -430,6 +430,7 @@ 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 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` rewrite type and apply the other values on hidden objects and in hidden layers and groups, which stay hidden unless a visibility value shows them, so a layer shown later holds the selected data set's text; objects that are locked or in a locked layer or group are skipped.
   - 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.
+  - Variables: when no object is bound to a variable that the data set has a value for, for example after Import Data Sets… defines new variables without binding them, choosing the data set in the Variables panel or stepping to it with the panel's arrows shows a status message, and `dataset.select`, `dataset.next` and `dataset.prev` add the message to the reply as `warning`.
   - Variables: Lock Variables (`variable.lock`, in the Variables panel's bottom bar and menu) stops variables from being defined, deleted or renamed until they are unlocked, while objects can still be bound and unbound and data sets still change and apply; the lock is saved with the document.
   - Batch…: Override Save and Override Export name each file with the extension of the format the step writes, however the step spells the format (`.svg` and `SVG` give `.svg`, `png8` gives `.png`), in `action.batch`.
   - Actions panel (record/playback, persisted), generic parameter dialogs for every "…" command.