#766: deliver ScriptUI mouse events to script listeners

Problem: ScriptUI controls never sent mouse events to scripts.
addEventListener("mousedown" | "mouseup" | "mousemove" | "mouseover" |
"mouseout" | "click") listeners never ran, so custom-drawn controls
(onDraw + mouse, as DuScriptUI builds them) could not react to the pointer.
docs/plugins.md listed this as missing.

Fix: scriptui.js builds a ScriptUI MouseEvent (clientX/clientY relative to
the target, button, detail = click count, screenX/Y, modifier keys,
getModifierState, stopPropagation, preventDefault) and delivers it in the
capture, target and bubble phases. addEventListener takes the capture flag.
The parent walk is bounded, so a script-made parent cycle cannot hang it.
Each published control lists the mouse events a listener wants
(Widget::mouse, inherited from containers). The new scriptui.mouse
command dispatches one event with clamped, finite values and rejects
unknown types and disabled controls. The egui ScriptUI view hit-tests the
pointer over script windows and docked panels, skipping covered layers and
windows blocked by a modal dialog. It sends mouseover/mouseout,
mousemove, mousedown/mouseup with click counts, and a click carrying the
pointer details in place of the plain click, so a checkbox still toggles
once. Handlers run under the existing script limits; a throwing listener
reports an error and the window keeps working.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/agents.md

@@ -512,7 +512,10 @@ Scripts that build ScriptUI windows publish them to the session; agents drive th
 3. `scriptui.click {"widget": "ok"}` presses a button / toggles a checkbox / picks a radio button or
    tab; `scriptui.set {"widget": "#4", "value": "Shot_"}` types into edit text, moves a slider or
    picks a list item (index or text); `scriptui.close {"result": 2}` closes. Controls are addressed
-   by id, `#id`, `properties.name` or text; `window` can be omitted when one window is open. Each
+   by id, `#id`, `properties.name` or text; `window` can be omitted when one window is open.
+   `scriptui.mouse {"widget": "pad", "type": "mousedown", "x": 10, "y": 20}` sends a mouse event
+   (`mousedown`, `mouseup`, `mousemove`, `mouseover`, `mouseout`, `click`; `x`/`y` relative to the
+   control, `button`, `detail`, `shiftKey`…) to the script's `addEventListener` listeners. Each
    returns the handler run's `{ok, output, error}`.
 
 A dialog's `show()` waits for the user: the `script.run` / `file.runScript` reply carries