Improvements to agent chat markdown rendering. (#6507)

### To test

- Ask the agent to “list all the things you can do and put them in a
markdown table”. I know we’re explicitly asking it for markdown, but I
don’t want to update the system prompt to ask it to make tables when
necessary because it’ll probably turn everything into a table, not sure
though, we can test in future.
     -  Notice how the loading is different
- Notice how the user chat is in a bubble but the agent chat is flat
(super standard design practice in AI tools, and looks much better when
the agent outputs mardown, expecially tables and needs room to do so)
- Ask it to do something different, then close the chat, and see that
the agent is marked as running and has a green outline and a green dot.
     - Play around with resizing the chat to make it bigger/smaller    
    
Open to any and all criticisms on any of the design choices, and of
course the usual, code etc.


Resizing
<img width="1572" height="812" alt="Screenshot 2026-06-01 at 2 47 53 PM"
src="https://github.com/user-attachments/assets/ec0ac1d0-01da-4025-bf7e-eea4eb544181"
/>

Loading (cool animation not visible through screenshot obviously)
<img width="559" height="141" alt="Screenshot 2026-06-01 at 2 53 41 PM"
src="https://github.com/user-attachments/assets/99f0b1f5-1719-4d78-8947-21b142293052"
/>

Removed bubbles for agent chat (maybe controversial, let me know) and
markdown now renders properly again
<img width="654" height="1060" alt="Screenshot 2026-06-01 at 2 55 01 PM"
src="https://github.com/user-attachments/assets/445f0889-a632-4751-9a16-f80ae388c632"
/>

frontend/editor/src/proprietary/components/chat/ChatPanel.css

@@ -61,6 +61,23 @@
   background: var(--mantine-color-blue-light);
   color: var(--mantine-color-blue-filled);
   flex-shrink: 0;
+  position: relative;
+}
+
+.chat-panel__agent-pill--loading {
+  border-color: color-mix(
+    in srgb,
+    var(--mantine-color-blue-5) 60%,
+    var(--border-subtle)
+  );
+}
+
+[data-mantine-color-scheme="dark"] .chat-panel__agent-pill--loading {
+  border-color: color-mix(
+    in srgb,
+    var(--mantine-color-blue-4) 55%,
+    var(--border-subtle)
+  );
 }
 
 /* Dark-mode: let the pill blend into the rail. Just a thin border, no fill —
@@ -284,15 +301,75 @@
 
 .chat-message-user {
   justify-content: flex-end;
+  margin: 0.2rem 0;
+}
+
+.chat-message-user__inner {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-end;
+  max-width: 85%;
 }
 
 .chat-message-assistant {
   justify-content: flex-start;
 }
 
-/* Bubble styling */
+/* Hover action row — copy, like, timestamp */
+.chat-message-actions {
+  display: flex;
+  align-items: center;
+  gap: 0.15rem;
+  margin-top: 0.3rem;
+  opacity: 0;
+  transition: opacity 120ms ease-out;
+  pointer-events: none;
+}
+
+.chat-message:hover .chat-message-actions,
+.chat-message-actions:focus-within {
+  opacity: 1;
+  pointer-events: auto;
+}
+
+.chat-message-action-btn {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  width: 1.5rem;
+  height: 1.5rem;
+  padding: 0;
+  border: none;
+  border-radius: 0.375rem;
+  background: transparent;
+  color: var(--text-muted);
+  cursor: pointer;
+  transition:
+    background 100ms ease-out,
+    color 100ms ease-out;
+}
+
+.chat-message-action-btn:hover {
+  background: var(--mantine-color-default-hover);
+  color: var(--mantine-color-text);
+}
+
+.chat-message-action-btn--active {
+  color: var(--mantine-color-blue-filled);
+}
+
+.chat-message-timestamp {
+  font-size: 0.7rem;
+  color: var(--text-muted);
+  padding: 0 0.25rem;
+  white-space: nowrap;
+}
+
+/* Bubble styling — user only */
+
 .chat-bubble {
-  max-width: 85%;
+  width: fit-content;
+  max-width: 100%;
 }
 
 .chat-bubble-user {
@@ -304,6 +381,87 @@
   color: white !important;
 }
 
+/* Assistant messages: no bubble, free-flowing with side padding */
 .chat-bubble-assistant {
-  background: var(--mantine-color-default-hover) !important;
+  width: 100%;
+  padding: 0 0.5rem;
+  font-size: var(--mantine-font-size-sm);
+}
+
+.chat-bubble-assistant p {
+  margin: 0 0 0.5em;
+}
+
+.chat-bubble-assistant p:last-child {
+  margin-bottom: 0;
+}
+
+/* Thinking indicator */
+.chat-thinking {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  padding: 0.125rem 0.5rem;
+  color: var(--mantine-color-blue-filled);
+}
+
+/* ─── Stirling logo thinking animation ─────────────────────────────────── */
+
+.stirling-thinking__path-right {
+  animation: stirling-orbit-right 2s ease-in-out infinite;
+}
+
+.stirling-thinking__path-left {
+  animation: stirling-orbit-left 2s ease-in-out infinite;
+}
+
+@keyframes stirling-orbit-right {
+  0%,
+  100% {
+    transform: translate(0, 0);
+    opacity: 0.5;
+  }
+  25% {
+    transform: translate(-1px, -5px);
+    opacity: 0.45;
+  }
+  50% {
+    transform: translate(-6px, 0);
+    opacity: 0.9;
+  }
+  75% {
+    transform: translate(-1px, 5px);
+    opacity: 0.55;
+  }
+}
+
+@keyframes stirling-orbit-left {
+  0%,
+  100% {
+    transform: translate(0, 0);
+    opacity: 1;
+  }
+  25% {
+    transform: translate(1px, 5px);
+    opacity: 0.85;
+  }
+  50% {
+    transform: translate(6px, 0);
+    opacity: 0.5;
+  }
+  75% {
+    transform: translate(1px, -5px);
+    opacity: 0.85;
+  }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .stirling-thinking__path-right {
+    animation: none;
+    opacity: 0.5;
+  }
+  .stirling-thinking__path-left {
+    animation: none;
+    opacity: 1;
+  }
 }