feat(design-mode): exit to pure-code mode when LP wasn't open at entry

The design-mode toggle now remembers whether live preview was open when
entering. If LP was already open the exit behavior is unchanged — LP
stays visible at its prior width. If LP was closed and got opened only
because design mode needed it, exiting closes LP again and main-toolbar
shrinks back to the icon-bar width, returning the user to the pure
code-editing layout they started from.

The skipToolbarRestore path (LP was just closed by the user via
toolbar-go-live) is unaffected — no double-close.

Updates section-5 tests so the two branches are explicit mirrors of
each other: LP-was-open keeps LP visible with toolbar at LP width;
LP-wasn't-open closes LP with toolbar at icon-bar width.

Author: abose

src/view/CentralControlBar.js

@@ -271,7 +271,20 @@ define(function (require, exports, module) {
             }
             _applyCollapsedLayout();
         } else {
-            _restoreExpandedLayout(skipToolbarRestore);
+            // If live preview was NOT open before we entered design mode,
+            // exit into pure-code mode by closing it again. Snapshot the
+            // entry state before _restoreExpandedLayout resets it.
+            // skipToolbarRestore is already the LP-just-closed path, so
+            // don't double-close in that case. _restoreExpandedLayout runs
+            // first so our !important geometry overrides are cleared before
+            // WorkspaceManager resizes #main-toolbar to the no-panel state.
+            const shouldCloseLivePreview = !skipToolbarRestore &&
+                !livePreviewWasOpen &&
+                _isLivePreviewOpen();
+            _restoreExpandedLayout(shouldCloseLivePreview ? true : skipToolbarRestore);
+            if (shouldCloseLivePreview) {
+                CommandManager.execute(Commands.FILE_LIVE_FILE_PREVIEW);
+            }
         }
     }
 

test/spec/CentralControlBar-integ-test.js

@@ -570,11 +570,19 @@ define(function (require, exports, module) {
                     "sidebar to settle at baseline 200px", 2000);
             });
 
-            it("should leave Live Preview open after exit", async function () {
+            it("should leave Live Preview open after exit when LP was already open at entry", async function () {
+                // Mirror of the "LP was opened by the toggle" test below: when
+                // the user already had LP open, exiting design mode must keep
+                // LP visible and main-toolbar at a real LP-panel width (well
+                // above the icon-bar width).
                 await openLivePreview();
                 await enterDesignMode();
                 await exitDesignMode();
+
                 expect(livePanel().isVisible()).toBe(true);
+                const iconsW = _$("#plugin-icons-bar").outerWidth();
+                const toolbarW = _$("#main-toolbar").outerWidth();
+                expect(toolbarW).toBeGreaterThan(iconsW + 50);
             });
 
             it("should fit sidebar + CCB + toolbar + a reasonable editor area in the window after exit", async function () {
@@ -591,17 +599,20 @@ define(function (require, exports, module) {
                 expect(testWindow.innerWidth - total).toBeGreaterThan(100);
             });
 
-            it("should use the innerWidth/2.5 default for toolbar when LP was opened by the toggle itself", async function () {
-                // LP is closed on entry — the toggle opens it.
+            it("should close Live Preview and shrink toolbar to the icon-bar width when LP was opened by the toggle itself", async function () {
+                // LP is closed on entry — the toggle opens it. On exit we
+                // restore the original "pure code" layout: LP closes again
+                // and main-toolbar shrinks to the icon-bar width.
                 await enterDesignMode();
+                expect(livePanel().isVisible()).toBe(true);
                 await exitDesignMode();
 
-                expect(livePanel().isVisible()).toBe(true);
-                const expectedDefault = Math.floor(testWindow.innerWidth / 2.5);
-                // `_restoreExpandedLayout` may trim a bit to honour the MIN_EDITOR clamp
-                // on narrow viewports, so compare with a generous tolerance.
-                const toolbar = _$("#main-toolbar").outerWidth();
-                expect(Math.abs(toolbar - expectedDefault)).toBeLessThan(30);
+                await awaitsFor(function () { return !livePanel().isVisible(); },
+                    "live preview to close on exit", 5000);
+
+                const iconsW = _$("#plugin-icons-bar").outerWidth();
+                const toolbarW = _$("#main-toolbar").outerWidth();
+                expect(Math.abs(toolbarW - iconsW)).toBeLessThan(3);
             });
 
             it("should not let the sidebar snap wider than the rendered (capped) width after exit even if user dragged past the cap in design mode", async function () {