fix(studio): keep the preview alive when the window is tight (#3091)

Panel sizes are reconciled against the window on every resize, with the preview holding a 360x200 floor that panels yield to before it gives.

Measured preview pane: 760px window 192 -> 433, 560px window 2 -> 516. Windows at or above 1280px are unchanged.

- fitPanels owns the who-yields decision for both axes
- panel caps are window-relative, replacing a flat 600px inspector cap
- below 860 the sidebar rails, below 700 the inspector collapses too
- auto-collapse is derived render state and never writes leftCollapsed
  (localStorage) or rightCollapsed (synced into the shareable URL)
- the rail and header toggles act on the effective state, so neither is a
  dead click that silently persists a collapse the user never asked for

packages/studio/src/App.tsx

@@ -399,7 +399,7 @@ export function StudioApp() {
   } = useInspectorState(
     panelLayout.rightPanelTab,
     panelLayout.rightInspectorPanes,
-    panelLayout.rightCollapsed,
+    panelLayout.effectiveRightCollapsed,
     isPlaying,
     domEditSession.domEditSelection,
     gestureState === "recording",
@@ -512,7 +512,7 @@ export function StudioApp() {
                       />
                     }
                     right={
-                      panelLayout.rightCollapsed ? null : (
+                      panelLayout.effectiveRightCollapsed ? null : (
                         <StudioRightPanel
                           designPanelActive={designPanelActive}
                           activeBlockParams={activeBlockParams}