Improve edge-docked window behavior (#2779)

* Make edge-docked windows resizable

Add draggable resize seams for left and right docked windows.

Keep the main chat area from getting too narrow and remember each window's dock width.

* Show emoji shortcodes as icons by default

Keep text-only emoji mode opt-in so model output like 😊 goes through the normal emoji renderer.

* Fix dock resize seams and left dock layout

Hide the resize seam when another floating modal is open, and keep the left-docked window from covering the chat area.

* Keep narrow modal tabs usable

* Fix split layout with both edge docks

* Fix left snap after right dock

* Enable left edge snap for all windows

* Tighten dock resize handle observers

* Use edge docking for settings window

static/js/windowDrag.js

@@ -93,11 +93,11 @@ export function makeWindowDraggable(modal, options = {}) {
   }
 
   const rightDock = enableDock ? makeEdgeDockController(modal, 'right') : null;
-  // Left dock is opt-in (enableLeftDock). For most windows it's off — the
-  // sidebar lives on the left, so a left dock collides with it. The email
-  // window enables it so you can park the message on the left and read it
-  // while replying in the document on the right.
-  const leftDock = (enableDock && options.enableLeftDock) ? makeEdgeDockController(modal, 'left') : null;
+  // Left dock is enabled by default too. modalSnap collapses the wide sidebar
+  // and anchors the panel beside the icon rail, so it no longer collides with
+  // the navigation. Callers can still pass enableLeftDock:false for a special
+  // modal that should only dock right.
+  const leftDock = (enableDock && options.enableLeftDock !== false) ? makeEdgeDockController(modal, 'left') : null;
 
   // Per-drag state, reset on mousedown.
   let dragging = false;