fix(ui-conversation): keep the summary suffix on one line

`flex: none` stops the `+n` box shrinking but not its text wrapping, so a
row too narrow for title + separator + suffix broke the one-line summary in
the exact case the slot exists for. Add `white-space: nowrap` and pin the
declaration as CSS text, since jsdom has no layout.

Also align the README's row illustration with the English rendering (the
same sentence's plan-strip clause already used it), and record the two
deferred review findings in the Agent Note so they survive merge.

packages/client/ui-conversation/tests/tool-row-styles.spec.ts

@@ -0,0 +1,42 @@
+/**
+ * The one-line contract of the ToolRow summary line as CSS text. jsdom has no
+ * layout, so the rendering specs (chat-tool-row.spec.tsx) can pin which spans
+ * exist but not whether a narrow row still fits on one line; these read the
+ * declarations the layout depends on.
+ */
+import { readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+
+const css = readFileSync(fileURLToPath(new URL('../src/client/chat/ToolRow.module.css', import.meta.url)), 'utf8')
+/** Declarations only: the sheet's prose names the properties it explains. */
+const declarationText = css.replace(/\/\*[\s\S]*?\*\//g, ' ')
+
+function declarations(selector: string): string[] {
+  const rule = new RegExp(`\\${selector}\\s*\\{([^{}]*)\\}`).exec(declarationText)
+  if (rule === null) throw new Error(`ToolRow.module.css has no \`${selector}\` rule`)
+  return (rule[1] ?? '').split(';').map(part => part.trim()).filter(Boolean)
+}
+
+describe('ToolRow.module.css summary line', () => {
+  it('keeps the summary suffix on one line and unshrunk', () => {
+    // `flex: none` stops the box shrinking, not the text wrapping: without
+    // `nowrap`, a row too narrow for title + separator + suffix wraps the `+n`
+    // onto a second line — the exact case the slot exists to survive.
+    expect(declarations('.summarySuffix')).toEqual(expect.arrayContaining([
+      'flex: none',
+      'white-space: nowrap',
+    ]))
+  })
+
+  it('leaves the truncation to the summary text alone', () => {
+    // The suffix must never ellipsize: a clipped count reads as a smaller
+    // number rather than as missing information.
+    expect(declarations('.summary')).toEqual(expect.arrayContaining([
+      'overflow: hidden',
+      'text-overflow: ellipsis',
+      'white-space: nowrap',
+    ]))
+    expect(declarations('.summarySuffix')).not.toEqual(expect.arrayContaining(['text-overflow: ellipsis']))
+  })
+})