fix(tui): wrap panel-sizing memos in altimate_change markers; per-test renderer isolation; derive contentWidth from panelAvailable

- Marker Guard: home.tsx panelAvailable and session contentWidth/panelAvailable
  are edits in upstream-shared files, now wrapped in altimate_change markers
- derive contentWidth from panelAvailable().width — one definition, can't drift
- render test: own the renderer per test (destroy + reset in finally) instead of
  a shared module-level var, safe under parallel bun test

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: saravmajestic

packages/tui/src/routes/home.tsx

@@ -68,9 +68,11 @@ export function Home() {
     if (configured === "auto") return Math.max(75, Math.floor(dimensions().width * 0.7))
     return configured ?? 75
   })
-  // Panel's available space (terminal minus this route's padding + vertical
-  // reserve). Shared arithmetic in welcome-panel-utils so tests exercise it.
+  // altimate_change start — WelcomePanel responsive sizing (#1067): the panel's
+  // available space = terminal minus this route's padding + vertical reserve.
+  // Shared arithmetic in welcome-panel-utils so the tests exercise it.
   const panelAvailable = createMemo(() => homeAvailable(dimensions().width, dimensions().height))
+  // altimate_change end
   let sent = false
 
   onMount(() => {

packages/tui/src/routes/session/index.tsx

@@ -272,15 +272,15 @@ export function Session() {
     return false
   })
   const showTimestamps = createMemo(() => timestamps() === "show")
-  const contentWidth = createMemo(
-    () => dimensions().width - (sidebarVisible() ? SIDEBAR_WIDTH : 0) - PANEL_HORIZONTAL_PADDING,
-  )
-  // Welcome panel's available space — same content-column basis as contentWidth
-  // (narrows with the sidebar whenever open, incl. the dimmed overlay on narrow
-  // terminals) so the panel stays aligned with the messages and both restore
-  // together when it closes. Height reserves the prompt row. Shared arithmetic in
-  // welcome-panel-utils so the tests exercise this exact math.
+  // altimate_change start — WelcomePanel responsive sizing (#1067). panelAvailable is the single
+  // source of the panel's usable size (via welcome-panel-utils, unit-tested); it narrows with the
+  // sidebar whenever open — including the dimmed full-area overlay on narrow terminals — so the
+  // panel and the messages stay aligned and both restore to full width when it closes. contentWidth
+  // (the shared content-column width) derives from it, so the width math has one definition and the
+  // two cannot structurally drift.
   const panelAvailable = createMemo(() => sessionAvailable(dimensions().width, dimensions().height, sidebarVisible()))
+  const contentWidth = createMemo(() => panelAvailable().width)
+  // altimate_change end
   const providers = createMemo(() => Model.index(sync.data.provider))
 
   const scrollAcceleration = createMemo(() => getScrollAcceleration(tuiConfig))

packages/tui/test/component/welcome-panel.test.tsx

@@ -1,6 +1,6 @@
 /** @jsxImportSource @opentui/solid */
 import { testRender } from "@opentui/solid"
-import { afterEach, expect, test } from "bun:test"
+import { expect, test } from "bun:test"
 import { resetSetupComplete } from "../../src/component/altimate-onboarding"
 import { WelcomePanel } from "../../src/component/welcome-panel"
 import { TuiConfigProvider } from "../../src/config"
@@ -67,31 +67,37 @@ async function renderPanel(availableWidth: number, availableHeight: number) {
   return { app, frame }
 }
 
-let current: Awaited<ReturnType<typeof testRender>> | undefined
-afterEach(() => {
-  current?.renderer.destroy()
-  current = undefined
-})
+// Own the renderer per test and destroy it in the same test's finally (plus reset
+// onboarding state), so nothing leaks between tests or races under parallel bun test.
+async function withPanel(width: number, height: number, check: (frame: string) => void) {
+  const { app, frame } = await renderPanel(width, height)
+  try {
+    check(frame)
+  } finally {
+    app.renderer.destroy()
+    resetSetupComplete()
+  }
+}
 
 test("full variant renders the wordmark + what-is section at a large available size", async () => {
-  const { app, frame } = await renderPanel(FULL_MIN_WIDTH, FULL_MIN_HEIGHT)
-  current = app
-  // "What is Altimate Code" is unique to the full two-column box.
-  expect(frame).toContain("What is Altimate Code")
+  await withPanel(FULL_MIN_WIDTH, FULL_MIN_HEIGHT, (frame) => {
+    // "What is Altimate Code" is unique to the full two-column box.
+    expect(frame).toContain("What is Altimate Code")
+  })
 })
 
 test("medium variant renders the condensed line (no what-is section) below the full width floor", async () => {
-  const { app, frame } = await renderPanel(FULL_MIN_WIDTH - 1, FULL_MIN_HEIGHT)
-  current = app
-  expect(frame).toContain("Gives your AI real context")
-  expect(frame).not.toContain("What is Altimate Code")
+  await withPanel(FULL_MIN_WIDTH - 1, FULL_MIN_HEIGHT, (frame) => {
+    expect(frame).toContain("Gives your AI real context")
+    expect(frame).not.toContain("What is Altimate Code")
+  })
 })
 
 test("compact variant renders a single line below the medium width floor", async () => {
-  const { app, frame } = await renderPanel(MEDIUM_MIN_WIDTH - 1, FULL_MIN_HEIGHT)
-  current = app
-  // Unconnected → the connect CTA; neither the medium nor full body is present.
-  expect(frame).toContain("Connect your AI model to start")
-  expect(frame).not.toContain("Gives your AI real context")
-  expect(frame).not.toContain("What is Altimate Code")
+  await withPanel(MEDIUM_MIN_WIDTH - 1, FULL_MIN_HEIGHT, (frame) => {
+    // Unconnected → the connect CTA; neither the medium nor full body is present.
+    expect(frame).toContain("Connect your AI model to start")
+    expect(frame).not.toContain("Gives your AI real context")
+    expect(frame).not.toContain("What is Altimate Code")
+  })
 })