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,
   }
 }

src/client/layout.css

@@ -47,10 +47,9 @@
   /* Grid/flex items default to min-height:auto. A long unbreakable token
      (OAuth URL) then grows this column past the viewport and clips the
      composer + left-rail Settings row. min-height:0 lets the cell shrink;
-     overflow:hidden keeps paint inside the cell; overflow-wrap wraps the
-     token so it cannot force the cell's intrinsic size. */
+     overflow-wrap lets the token wrap instead of forcing its intrinsic
+     size. The host's own descendants remain responsible for scrolling. */
   min-height: 0;
-  overflow: hidden;
   overflow-wrap: anywhere;
   transition: margin-bottom var(--ds-transition-duration-slow) var(--ds-ease-in-out);
 }

tests/layout-css.spec.ts

@@ -16,7 +16,14 @@ describe('layout.css conversation column', () => {
 
   it('allows the center column to shrink and wrap long tokens', () => {
     expect(css).toMatch(/min-height:\s*0/)
-    expect(css).toMatch(/overflow:\s*hidden/)
     expect(css).toMatch(/overflow-wrap:\s*anywhere/)
   })
+
+  it('leaves overflow ownership to the host conversation descendants', () => {
+    const conversationRule = css.match(
+      /#root \[data-dsh-frame\][\s\S]*?\{([\s\S]*?)\n\}/,
+    )?.[1]
+    expect(conversationRule).toBeDefined()
+    expect(conversationRule).not.toMatch(/(?:^|[;\s])overflow\s*:/)
+  })
 })

tests/layout-push.spec.ts

@@ -72,4 +72,28 @@ describe('layoutPushSize', () => {
       viewportHeight: 800,
     })).toEqual({ width: 400, height: 220 })
   })
+
+  it('never pushes beyond a viewport smaller than the normal panel minima', () => {
+    expect(layoutPushSize({
+      narrow: false,
+      panelOpen: true,
+      bottomOpen: true,
+      width: 400,
+      bottomHeight: 220,
+      viewportWidth: 200,
+      viewportHeight: 200,
+    })).toEqual({ width: 200, height: 0 })
+  })
+
+  it('turns non-finite geometry into a safe zero push', () => {
+    expect(layoutPushSize({
+      narrow: false,
+      panelOpen: true,
+      bottomOpen: true,
+      width: Number.NaN,
+      bottomHeight: Number.POSITIVE_INFINITY,
+      viewportWidth: Number.NaN,
+      viewportHeight: Number.POSITIVE_INFINITY,
+    })).toEqual({ width: 0, height: 0 })
+  })
 })