Variables: a visibility variable shows and hides locked art

variable.bind refused a locked layer, a locked object and objects
inside a locked layer or group for every kind of variable, and
dataset.select skipped them. A visibility variable bound before the
art was locked stopped working, and a locked layer could not be shown
or hidden by a data set.

A visibility variable now binds locked art and objects inside a locked
layer or group. dataset.select, dataset.next and dataset.prev show and
hide them and leave them locked. dataset.list, dataset.capture and
dataset.update read whether they show. Text, image and graph variables
are refused for locked art as before, and a row skips them. Binding
any variable still refuses art inside a hidden layer or group, and for
a visibility variable the error says the art is in a hidden group or
layer.

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

docs/mcp.md

@@ -1156,11 +1156,15 @@ already walks Image Trace. Short agent entry points:
 `dataset.select`, `dataset.next` and `dataset.prev` reply `{name, applied, skipped}`. They add `overflow: [id…]`
 when area type or type on a path whose text they rewrote doesn't fit, as `text.setText` does (see
 [Fitting area type](#fitting-area-type-auto-size-shrink-text-to-fit-overflow)). They skip an object that is
-locked or inside a locked layer or group, and count it in `skipped`. They rewrite hidden objects and objects inside
+locked or inside a locked layer or group, and count it in `skipped`, unless the value is a visibility value, which
+shows or hides it. They rewrite hidden objects and objects inside
 a hidden layer or group, which stay hidden unless one of the data set's visibility values shows them. When such a
 layer is shown again, its type holds the data set's text. They apply the values in the order the variables are
 defined. Of two variables of the same kind on one object, the one defined last wins. `dataset.list`,
-`dataset.capture` and `dataset.update` read hidden objects and objects inside a hidden layer or group as well.
+`dataset.capture` and `dataset.update` read hidden objects and objects inside a hidden layer or group as well, and
+read whether a locked object, or one inside a locked layer or group, shows. `variable.bind` binds a visibility
+variable to a locked layer or object and to objects inside a locked layer or group, and refuses them for a text,
+image or graph variable.
 
 ```json
 {"name":"run_command","arguments":{"command":"symbol.list","params":{}}}
@@ -1174,8 +1178,8 @@ defined. Of two variables of the same kind on one object, the one defined last w
 ```
 
 `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
+data set holds. A variable whose objects report no value, because they are deleted or, for a text, image or graph
+variable, locked or inside a locked layer or group, keeps the data set's value. With `all: true` it also adds every other variable that the
 objects report a value for. The reply gives `values`, the number of values it wrote, and `left`, the variables it
 did not write.
 

docs/target-app-parity.md

@@ -423,13 +423,14 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
 
 - **Architecture:** 19+ crates with enforced layering (`cargo xtask layers`). Every action is a command (~400 engine + ~50 UI). Undo is unlimited via structural sharing. `command.batch` runs several commands as one transaction.
 - **Automation:**
-  - 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: 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 text, image or graph 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, except by a visibility value.
+  - Variables: a visibility variable binds a locked layer, a locked object and objects inside a locked layer or group, and `dataset.select`, `dataset.next` and `dataset.prev` show and hide them without unlocking them; `dataset.list`, `dataset.capture` and `dataset.update` read whether they show. A text, image or graph variable refuses locked art.
   - 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: 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.
   - 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 (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 except by visibility values; 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.
   - Synthetic input validates complete gestures before queue mutation: at most 256 drag steps, 16 clicks and 1,024 pending events; up to 64 control requests per frame, with later requests retained for the next frame (#1709).