feat(tui): replace footer hints with model telemetry

tui/src/footer-hints.ts

@@ -1,6 +1,7 @@
 import { RGBA, StyledText, TextAttributes, type TextChunk } from "@opentui/core"
 
-import { optionArrowUp } from "./platform-keys"
+import { formatTokenCount } from "./context-panel"
+import type { TokenUsage } from "./protocol"
 
 export interface FooterHint {
   key: string
@@ -30,10 +31,63 @@ export function contextualFooterHints(
   mode: FooterMode,
   width: number,
   theme: FooterHintTheme,
-  platform: string = process.platform,
-  shiftedEnter = false,
+  _platform: string = process.platform,
+  _shiftedEnter = false,
 ): StyledText {
-  return footerHints(hintsFor(mode, width, platform, shiftedEnter), theme)
+  return footerHints(hintsFor(mode, width), theme)
+}
+
+/** Last-turn model telemetry. Passive chrome reports the system, not its manual. */
+export function footerTelemetry(
+  usage: TokenUsage | null,
+  width: number,
+  theme: FooterHintTheme,
+): StyledText {
+  if (!usage) return new StyledText([])
+  const parts: string[] = []
+  const duration = usage.generation_ms
+  const measured = usage.measured_completion_tokens
+  if (typeof duration === "number" && duration > 0 && typeof measured === "number") {
+    const rate = measured * 1000 / duration
+    const value = rate < 10 ? rate.toFixed(1) : String(Math.round(rate))
+    const estimated = (usage.estimated_tokens || 0) > 0 ? "~" : ""
+    parts.push(`${estimated}${value} tok/s`)
+  }
+  if (
+    typeof usage.cached_tokens === "number"
+    && typeof usage.prompt_tokens === "number"
+    && usage.prompt_tokens > 0
+  ) {
+    const hitRate = Math.min(100, Math.max(0, Math.round(
+      usage.cached_tokens * 100 / usage.prompt_tokens,
+    )))
+    parts.push(`cache ${hitRate}%`)
+  }
+  if (width >= 72) {
+    const prompt = usage.prompt_tokens
+    const completion = usage.completion_tokens
+    if (typeof prompt === "number" || typeof completion === "number") {
+      parts.push(`↑${formatTokenCount(prompt || 0)} ↓${formatTokenCount(completion || 0)}`)
+    }
+  }
+  if (width >= 112 && typeof usage.ttft_ms === "number") {
+    const requests = Math.max(1, usage.timed_requests || 1)
+    const average = usage.ttft_ms / requests
+    parts.push(`TTFT ${average < 1000 ? `${Math.round(average)}ms` : `${(average / 1000).toFixed(1)}s`}`)
+  }
+  if (width >= 128 && typeof usage.cost_usd === "number" && usage.cost_usd > 0) {
+    parts.push(`$${usage.cost_usd < 0.01 ? usage.cost_usd.toFixed(4) : usage.cost_usd.toFixed(2)}`)
+  }
+  return footerMetrics(parts, theme)
+}
+
+function footerMetrics(parts: readonly string[], theme: FooterHintTheme): StyledText {
+  const chunks: TextChunk[] = []
+  parts.forEach((text, index) => {
+    if (index) chunks.push(chunk(" · ", theme.separator))
+    chunks.push(chunk(text, index === 0 ? theme.accent : theme.muted, index === 0))
+  })
+  return new StyledText(chunks)
 }
 
 /** Give shortcuts visual hierarchy without turning the footer into a toolbar. */
@@ -51,8 +105,6 @@ export function footerHints(hints: readonly FooterHint[], theme: FooterHintTheme
 function hintsFor(
   mode: FooterMode,
   width: number,
-  platform: string,
-  shiftedEnter: boolean,
 ): FooterHint[] {
   if (mode === "runtime") return width >= 64
     ? [hint("↑↓/click", "choose"), hint("enter", "apply"), hint("esc", "close")]
@@ -60,9 +112,7 @@ function hintsFor(
   if (mode === "mention") return width >= 64
     ? [hint("↑↓", "choose"), hint("tab/enter", "insert"), hint("esc", "close")]
     : [hint("enter", "insert"), hint("esc", "close")]
-  if (mode === "active") return width >= 96
-    ? [hint("enter", "steer"), hint("tab", "queue"), hint(optionArrowUp(platform), "edit"), stopHint()]
-    : width >= 64 ? [hint("enter", "steer"), hint("tab", "queue"), stopHint()] : []
+  if (mode === "active") return []
   if (mode === "branch") return width >= 64
     ? [hint("type", "filter"), hint("↑↓", "choose"), hint("enter", "branch"), hint("esc", "close")]
     : [hint("enter", "branch"), hint("esc", "close")]
@@ -76,26 +126,13 @@ function hintsFor(
   if (mode === "history") return width >= 72
     ? [hint("ctrl+end", "latest"), hint("pgup/pgdn", "scroll")]
     : width >= 48 ? [hint("ctrl+end", "latest")] : []
-  const newline = shiftedEnter ? "shift+enter" : "ctrl+j"
-  if (width >= 112) return [
-    hint("enter", "send"),
-    hint(newline, "newline"),
-    hint("pgup/pgdn", "scroll"),
-    hint("ctrl+o", "tools"),
-    stopHint(),
-  ]
-  if (width >= 72) return [hint("enter", "send"), hint(newline, "newline"), stopHint()]
-  return width >= 48 ? [hint("enter", "send"), hint(newline, "newline")] : []
+  return []
 }
 
 function hint(key: string, label: string): FooterHint {
   return { key, label }
 }
 
-function stopHint(): FooterHint {
-  return { key: "ctrl+c", label: "stop", tone: "danger" }
-}
-
 function chunk(text: string, color: string, bold = false): TextChunk {
   return {
     __isChunk: true,