fix: harden layout push bounds

src/client/layout-push.ts

@@ -3,7 +3,7 @@
  * The conversation column (output + composer) must keep at least
  * {@link PANEL_MIN} of the viewport after the bottom panel claims height.
  */
-import { BOTTOM_MIN, PANEL_MIN } from './state.ts'
+import { PANEL_MIN } from './state.ts'
 
 export interface LayoutPushInput {
   narrow: boolean
@@ -20,13 +20,18 @@ export interface LayoutPushSize {
   height: number
 }
 
+function finiteNonNegative(value: number): number {
+  return Number.isFinite(value) ? Math.max(0, value) : 0
+}
+
 /** Compute the live layout-push size. Narrow drawers float and push 0. */
 export function layoutPushSize(input: LayoutPushInput): LayoutPushSize {
   if (input.narrow) return { width: 0, height: 0 }
-  const maxWidth = Math.max(PANEL_MIN, input.viewportWidth)
-  const maxHeight = Math.max(BOTTOM_MIN, input.viewportHeight - PANEL_MIN)
+  const viewportWidth = finiteNonNegative(input.viewportWidth)
+  const viewportHeight = finiteNonNegative(input.viewportHeight)
+  const maxHeight = Math.max(0, viewportHeight - Math.min(PANEL_MIN, viewportHeight))
   return {
-    width: input.panelOpen ? Math.min(Math.max(0, input.width), maxWidth) : 0,
-    height: input.bottomOpen ? Math.min(Math.max(0, input.bottomHeight), maxHeight) : 0,
+    width: input.panelOpen ? Math.min(finiteNonNegative(input.width), viewportWidth) : 0,
+    height: input.bottomOpen ? Math.min(finiteNonNegative(input.bottomHeight), maxHeight) : 0,
   }
 }