Per user report — the tag's mode metadata coincided with a
500 error on agent mode (especially on mobile). Removing the
UI tag, the chat.js writes of metadata.mode, and the CSS pill
so agent mode posts work cleanly again.
Touches:
- chat.js: drop _sendMode capture + meta.mode writes (user + assistant)
- chatRenderer.js: roleTimestamp() back to a single (when) arg, drop
the .role-mode-tag append; updated three call sites
- style.css: dropped .role-mode-tag and .role-mode-agent rules
c822d34ce6