Guides: a Cmd/Ctrl+Shift double-click releases the guide under the pointer

A double-click on a ruler guide with the Selection, Direct Selection or
Group Selection tool did nothing, whatever keys were held. A guide could
be released only with View › Guides › Release Guides.

With the Selection, Direct Selection or Group Selection tool, a
double-click with Cmd/Ctrl and Shift held now runs view.guides.release
on the ruler guide under the pointer (index) or, when no ruler guide
is there, on the guide path under it (ids). Nothing is released while
guides are hidden or locked, and a double-click without both keys does
what it did before.

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

docs/mcp.md

@@ -1067,7 +1067,10 @@ Otherwise it releases the selected guide paths and ruler guides, and with no gui
 path. A released ruler guide becomes a straight path with no fill or stroke, at the top of the guide's layer (or where
 new art goes, for a guide on no layer). An artboard guide becomes a line across its artboard, and a canvas guide
 becomes a line across the bounds of all the artboards. `index` and `ids` are refused while guides are locked. The
-release is one undo step, and the released paths are selected.
+release is one undo step, and the released paths are selected. With the Selection, Direct Selection or Group
+Selection tool, a double-click with Cmd/Ctrl and Shift held releases the ruler guide or guide path under the pointer
+(`pointer_gesture` with a `doubleclick` event and `mods: {cmd: true, shift: true}`), unless guides are hidden or
+locked.
 
 The Selection, Direct Selection and Group Selection tools pick a guide within the selection tolerance, over the art
 (an anchor on it comes first with Direct Selection), and drag the selected guides: `mods.alt` copies them,