revert(tui): drop DeferredMd, profiling showed it was neutral

Profiled with scripts/profile-tui.py under hold-PageUp + hold-wheel.
The placeholder → microtask-upgrade pattern did not reduce renderer
p99 (63ms → 63ms) or max (96ms → 142ms, slightly worse).  Each fresh
row still pays the Md cost — just on a follow-up commit instead of
inline — and the follow-up commit shows up as a second heavy frame
a few ms later.

The real bottlenecks turned out to be:

  1. wheel step too large (fixed in 7ca16eea)
  2. outer terminal ANSI parse throughput (diagnosing next)
  3. React commit frequency during hold-scroll (needs coalescing)

None of which DeferredMd addresses.  Clearing the complexity so the
next experiments land on a simpler substrate.

ui-tui/src/components/deferredMarkdown.tsx

@@ -1,90 +0,0 @@
-// DeferredMd — renders a lightweight <Text> placeholder on first mount and
-// upgrades to full <Md> markdown + syntax highlighting in a subsequent
-// transition commit. Spreads the parse cost off the scroll critical path.
-//
-// Why: profiling shows the 63-112ms renderer spikes during hold-PageUp
-// correlate with fresh MessageLine mounts running the markdown tokenizer
-// + syntax highlighting synchronously. The new row is added by
-// useVirtualHistory's slide step; React commits the tree; Ink lays out
-// Yoga; stdout writes the result. All in one hitch frame.
-//
-// With this wrapper, the hitch frame lays out a pre-wrapped plain <Text>
-// (Yoga only needs to wrap width-known strings — no tokenizer, no
-// highlighter, no inline regex walk), then a follow-up commit re-renders
-// the same row with full markdown. The follow-up is gated on a
-// queueMicrotask so Ink has a chance to paint the placeholder before
-// React starts the Md-heavy upgrade work.
-//
-// Upgrade cache: once a given (theme, text, compact) tuple has been
-// rendered as full Md, we remember it so remounts (scroll-out then
-// scroll-back) don't pay the placeholder round-trip again — they mount
-// straight into the upgraded <Md> subtree, which Md internally memoizes
-// on text identity, so there's no re-tokenization either.
-
-import { Text } from '@hermes/ink'
-import { memo, useEffect, useState } from 'react'
-
-import type { Theme } from '../theme.js'
-
-import { Md, stripInlineMarkup } from './markdown.js'
-
-// Theme object is stable per-session; key upgrades under it so palette
-// swaps naturally retrigger (colors differ → render changes).
-const upgraded = new WeakMap<Theme, Set<string>>()
-
-const cacheKey = (compact: boolean | undefined, text: string) => (compact ? `c:${text}` : `x:${text}`)
-
-const hasUpgraded = (t: Theme, key: string) => upgraded.get(t)?.has(key) ?? false
-
-const markUpgraded = (t: Theme, key: string) => {
-  const bucket = upgraded.get(t) ?? new Set<string>()
-
-  bucket.add(key)
-  upgraded.set(t, bucket)
-}
-
-export const DeferredMd = memo(function DeferredMd({ color, compact, t, text }: DeferredMdProps) {
-  const key = cacheKey(compact, text)
-  const [ready, setReady] = useState(() => hasUpgraded(t, key) || !text)
-
-  useEffect(() => {
-    if (ready) {
-      return
-    }
-
-    let cancelled = false
-
-    queueMicrotask(() => {
-      if (cancelled) {
-        return
-      }
-
-      markUpgraded(t, key)
-      setReady(true)
-    })
-
-    return () => {
-      cancelled = true
-    }
-  }, [key, ready, t])
-
-  if (ready) {
-    return <Md compact={compact} t={t} text={text} />
-  }
-
-  // Placeholder: strip inline markup so the visible width approximately
-  // matches the final Md layout (bold/italic/links are width-neutral or
-  // collapse to anchor text). Line breaks preserved — Ink's wrap="wrap"
-  // lays the plain text out as blocks at the right column count.
-  // Using <Text> directly (no Box wrapper) so there's no column-flex
-  // decision for Yoga — it just wraps a string.
-  return <Text color={color ?? undefined}>{stripInlineMarkup(text)}</Text>
-})
-
-interface DeferredMdProps {
-  /** Fallback color for the placeholder text (typically the role's body color). */
-  color?: string
-  compact?: boolean
-  t: Theme
-  text: string
-}

ui-tui/src/components/messageLine.tsx

@@ -9,7 +9,7 @@ import { boundedLiveRenderText, compactPreview, hasAnsi, isPasteBackedText, stri
 import type { Theme } from '../theme.js'
 import type { ActiveTool, DetailsMode, Msg, SectionVisibility } from '../types.js'
 
-import { DeferredMd } from './deferredMarkdown.js'
+import { Md } from './markdown.js'
 import { StreamingMd } from './streamingMarkdown.js'
 import { ToolTrail } from './thinking.js'
 import { TodoPanel } from './todoPanel.js'
@@ -107,12 +107,7 @@ export const MessageLine = memo(function MessageLine({
         // streamingMarkdown.tsx for the cost model.
         <StreamingMd compact={compact} t={t} text={boundedLiveRenderText(msg.text)} />
       ) : (
-        // Deferred markdown: plain-text placeholder on first mount, upgrade
-        // to full Md on a queued microtask. Spreads the tokenizer + syntax
-        // cost off the scroll critical path so hold-PageUp doesn't hitch
-        // on fresh assistant rows entering overscan. See
-        // deferredMarkdown.tsx for the trade-offs.
-        <DeferredMd color={body} compact={compact} t={t} text={msg.text} />
+        <Md compact={compact} t={t} text={msg.text} />
       )
     }
 

ui-tui/src/components/thinking.tsx

@@ -899,7 +899,7 @@ export const ToolTrail = memo(function ToolTrail({
     return duration ? (
       <>
         {label}
-        <Text color={t.color.dim} dim>
+        <Text color={t.color.statusFg} dim>
           {duration}
         </Text>
       </>