fix: improve activity rendering, spacing, and path truncation (#654)

* fix: polish activity tool rows and message spacing

Show each tool call as its own row in live and activity views
Keep tool descriptions inline with truncation and cleaner read-file paths
Tune spacing, todo counts, and bash timing display for clearer chat flow

* fix: refine activity tool rows and truncation behavior

Make activity collapse behavior consistent across modes and rename default mode label to Expanded
Show tool descriptions inline with improved spacing and one-row-per-tool rendering
Fix read/edit path truncation to clip from the start while keeping edit filenames highlighted

* fix: resolve chat activity lint regressions

Remove unused activity render mode state in message body
Mark path helper animation arg as intentionally unused to satisfy lint

packages/ui/src/components/chat/message/parts/AssistantTextPart.tsx

@@ -88,7 +88,10 @@ const AssistantTextPart: React.FC<AssistantTextPartProps> = ({
     }
 
     return (
-        <div className="group/assistant-text relative break-words" key={part.id || `${messageId}-text`}>
+        <div
+            className={`group/assistant-text relative break-words ${chatRenderMode === 'live' ? 'my-1' : ''}`}
+            key={part.id || `${messageId}-text`}
+        >
             <MarkdownRenderer
                 content={displayTextContent}
                 part={part}