feat: improve chat streaming UX and add Mermaid diagram rendering (#438)

* feat: show current branch in empty chat state

* fix: display current git branch for worktrees and update them with branch change

* refactor: improve read tool output parsing with structured data

* feat: add support for message part delta events

* fix(chat): improve streaming rendering, scroll behavior, and assistant action visibility

* feat: Add mermaid diagram support to chat markdown rendering

* fix: update table download functionality to include success notification and remove unused MarkdownRenderer import

* refactor: streamline Streamdown component props for improved readability

* fix: preserve Streamdown code-block markers and use native Tauri cache clearing

* feat: add context overview panel to view conversation details

packages/ui/src/index.css

@@ -864,6 +864,11 @@ html:not(.dark) .chat-scroll {
   contain-intrinsic-size: none !important;
 }
 
+/* Mermaid block: position context for controls wrapper. */
+[data-streamdown="mermaid-block"] {
+  position: relative;
+}
+
 /* Hide system caret in terminal - targets both Ghostty internal input and our custom touch input */
 .terminal-viewport-container textarea,
 .terminal-viewport-container input {