feat(web): opaque tooltip surface; drop redundant 'updated Nm ago' body

Two operator-feedback fixes on the new session-list HoverTooltip:

1. Tooltip background was bg-[var(--app-bg)] - the same variable as the
   session row underneath - so the tooltip looked translucent and the row
   text bled through. Switch to bg-[var(--app-secondary-bg)] (#2C2C2E
   dark / #f3f4f6 light, both opaque) and bump shadow-md -> shadow-lg.
   Telegram-themed clients still pick up tg-theme-secondary-bg-color so
   the tooltip stays on-theme.

2. The 'unread' attention dot tooltip rendered 'New activity / Updated 5m
   ago', but the relative-time pill ('5m ago') is already on the right
   edge of the same session row. The tooltip body just duplicated info.
   Render only the title for the unread case; drop the
   session.tooltip.unread.body i18n key from en + zh-CN.

The other tooltip kinds (permission/input list tools, background lists
task count) keep their bodies - those facts are not visible elsewhere on
the row.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: heavygee

web/src/components/HoverTooltip.tsx

@@ -48,8 +48,8 @@ export function HoverTooltip(props: {
                 id={id}
                 className={cn(
                     'pointer-events-none absolute z-30 max-w-[14rem] whitespace-normal',
-                    'rounded-md border border-[var(--app-border)] bg-[var(--app-bg)]',
-                    'px-2 py-1 text-xs leading-snug text-[var(--app-fg)] shadow-md',
+                    'rounded-md border border-[var(--app-border)] bg-[var(--app-secondary-bg)]',
+                    'px-2 py-1 text-xs leading-snug text-[var(--app-fg)] shadow-lg',
                     side === 'top' ? 'bottom-full mb-1' : 'top-full mt-1',
                     alignClasses,
                     'opacity-0 invisible',

web/src/components/SessionAttentionIndicator.test.tsx

@@ -166,7 +166,7 @@ describe('SessionAttentionIndicator tooltip', () => {
         expect(tooltip.textContent).toContain('3 tasks running')
     })
 
-    it('renders relative-time hint for unread attention', () => {
+    it('renders only the title for unread attention (relative time is already on the row)', () => {
         const updatedAt = Date.now() - 5 * 60_000
         const summary = makeSummary({
             id: 's1',
@@ -183,7 +183,8 @@ describe('SessionAttentionIndicator tooltip', () => {
 
         const tooltip = screen.getByRole('tooltip', { hidden: true })
         expect(tooltip.textContent).toContain('New activity')
-        expect(tooltip.textContent).toMatch(/Updated .+ ago|Updated just now/)
+        // The "Nm ago" pill in the session row already shows this; do not duplicate.
+        expect(tooltip.textContent).not.toMatch(/Updated /)
     })
 
     it('exposes aria-label on the dot for screen readers', () => {

web/src/components/SessionAttentionIndicator.tsx

@@ -3,7 +3,6 @@ import type { SessionAttention } from '@/lib/sessionAttention'
 import { getSessionAttentionLabelKey } from '@/lib/sessionAttention'
 import { useTranslation } from '@/lib/use-translation'
 import { HoverTooltip } from '@/components/HoverTooltip'
-import { formatRelativeTime } from '@/lib/relativeTime'
 
 const ATTENTION_DOT_CLASS: Record<SessionAttention['kind'], string> = {
     permission: 'bg-amber-500 animate-pulse',
@@ -122,16 +121,8 @@ function AttentionTooltipDetail(props: {
         )
     }
 
-    if (attention.kind === 'unread') {
-        const time = formatRelativeTime(summary.updatedAt, t)
-        if (!time) return null
-        return (
-            <span className="mt-1 block text-[var(--app-hint)]">
-                {t('session.tooltip.unread.body', { time })}
-            </span>
-        )
-    }
-
+    // 'unread' deliberately has no body: the relative-time pill is already
+    // rendered in the session row, so a tooltip body would just duplicate it.
     return null
 }
 

web/src/lib/locales/en.ts

@@ -114,7 +114,6 @@ export default {
   'session.tooltip.input.body': 'Reply to:',
   'session.tooltip.background.count.one': '1 task running',
   'session.tooltip.background.count.other': '{count} tasks running',
-  'session.tooltip.unread.body': 'Updated {time}',
   'session.tooltip.scheduled.body': 'Will fire when due.',
   'session.tooltip.moreCount': '+{count} more',
   'session.time.justNow': 'just now',

web/src/lib/locales/zh-CN.ts

@@ -114,7 +114,6 @@ export default {
   'session.tooltip.input.body': '回复:',
   'session.tooltip.background.count.one': '1 个任务运行中',
   'session.tooltip.background.count.other': '{count} 个任务运行中',
-  'session.tooltip.unread.body': '更新于 {time}',
   'session.tooltip.scheduled.body': '到时会自动发送。',
   'session.tooltip.moreCount': '另有 {count} 条',
   'session.time.justNow': '刚刚',