Merge main into feat/plugin-importers

docs/mcp.md

@@ -1812,7 +1812,8 @@ already walks Image Trace. Short agent entry points:
   first value at −180° to its second at 180°. A stroke without that input draws the brush's own value (a Scatter
   brush's value half way between the two).
 - Variables: `variable.list`, `variable.define {name, kind: text|visibility|image|graph}`, `variable.bind {variable, ids?}`,
-  `variable.makeTextDynamic`, `variable.makeVisibilityDynamic`, `variable.makeImageDynamic`, `variable.makeGraphDynamic`,
+  `variable.makeTextDynamic`, `variable.makeVisibilityDynamic`, `variable.makeImageDynamic`, `variable.makeGraphDynamic`
+  (`variable.bind` and `variable.makeTextDynamic` refuse type that already has another text variable and name it),
   `variable.unbind`, `variable.rename`, `variable.delete`, `variable.highlight` (image values are file paths, graph
   values CSV as `graph.setData`). `variable.lock {locked?}` (Lock Variables) locks or unlocks the variables;
   without `locked` it toggles, and the lock is saved with the document. While the variables are locked,

docs/target-app-parity.md

@@ -655,6 +655,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - Variables: Load Variable Library… in the Variables panel menu (`variable.loadLibrary`) replaces the document's variables and data sets with a variable library's, read from its XML file, in one undo step: every data set is deleted, and every variable is deleted with its bindings and values, except a text variable the library also declares, which stays bound so the library's data sets change its objects (#4136); then the library's other text variables are defined, unbound, and its data sets take the text of each value's `p` elements, one paragraph each. Variables of other kinds are left out with a warning that names their kinds.
   - Variables: Save Variable Library… in the Variables panel menu (`variable.saveLibrary`) writes the document's text variables and data sets as a variable library's XML file, which Load Variable Library reads back with the same text variables, data set names and text values. Variables of other kinds are left out with a warning that names their kinds.
   - JSON-lines control channel with real egui pointer and keyboard injection.
+  - Variables: a type object holds one text variable. `variable.bind` and Make Text Dynamic refuse a second one and name the text variable the object has; a visibility variable can still share the object, and a document saved with two text variables on one object opens with both.
   - 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).
   - The control server writes each reply through a 64 KiB buffer. On Windows 11 it sends the 17 MB `document.inspect` reply of a document with 50,000 objects on one layer to a client over loopback in 0.09 s instead of 34 s.
   - Parameter keys: the engine refuses a key that a command's params description doesn't name before the command runs, in every build and for every caller, including the app's own calls, the commands a command runs and the steps of `command.batch` and `action.batch`. An action recorded by an older version still plays from the Actions panel and the Batch dialog (`Session::replay`). `crates/engine/tests/it/param_keys.rs`.