bugfix: remove redundant thinking updates and put a thinking timer above the prompt instead (#216)

I had Codex read #182 and draft a PR to fix it. This is its suggested
approach. I've tested it and it works. It removes the purple `thinking
for 386s` type lines entirely, and replaces them with a single yellow
`thinking for #s` line:
```
thinking for 31s
╭────────────────────────────────────────╮
│(  ●   )  Thinking..      
╰────────────────────────────────────────╯
```
prompt. I've been using it that way via `npm run dev`, and prefer it.

## What

Empty "reasoning" updates were showing up as blank lines in the terminal
chat history. We now short-circuit and return `null` whenever
`message.summary` is empty, so those no-ops are suppressed.

## How

- In `TerminalChatResponseReasoning`, return early if `message.summary`
is falsy or empty.
- In `TerminalMessageHistory`, drop any reasoning items whose
`summary.length === 0`.
- Swapped out the loose `any` cast for a safer `unknown`-based cast.
- Rolled back the temporary Vitest script hacks that were causing stack
overflows.

## Why

Cluttering the chat with empty lines was confusing; this change ensures
only real reasoning text is rendered.
Reference: openai/codex#182

---------

Co-authored-by: Thibault Sottiaux <tibo@openai.com>

codex-cli/src/components/chat/terminal-message-history.tsx

@@ -30,16 +30,14 @@ const MessageHistory: React.FC<MessageHistoryProps> = ({
   thinkingSeconds,
   fullStdout,
 }) => {
-  const [messages, debug] = useMemo(
-    () => [batch.map(({ item }) => item!), process.env["DEBUG"]],
-    [batch],
-  );
+  // Flatten batch entries to response items.
+  const messages = useMemo(() => batch.map(({ item }) => item!), [batch]);
 
   return (
     <Box flexDirection="column">
-      {loading && debug && (
+      {loading && (
         <Box marginTop={1}>
-          <Text color="yellow">{`(${thinkingSeconds}s)`}</Text>
+          <Text color="yellow">{`thinking for ${thinkingSeconds}s`}</Text>
         </Box>
       )}
       <Static items={["header", ...messages]}>
@@ -48,8 +46,13 @@ const MessageHistory: React.FC<MessageHistoryProps> = ({
             return <TerminalHeader key="header" {...headerProps} />;
           }
 
-          // After the guard above `item` can only be a ResponseItem.
+          // After the guard above, item is a ResponseItem
           const message = item as ResponseItem;
+          // Suppress empty reasoning updates (i.e. items with an empty summary).
+          const msg = message as unknown as { summary?: Array<unknown> };
+          if (msg.summary?.length === 0) {
+            return null;
+          }
           return (
             <Box
               key={`${message.id}-${index}`}