Multi-turn conversation, stop generation, SSE fix, and UI improvements

- Multi-turn context: all council stages now receive conversation history
  (user messages + Stage 3 chairman responses) for coherent follow-ups
- Stop generation: abort streaming mid-request, recover query to input box
- SSE parsing: buffer-based chunking to prevent JSON split across packets
- Atomic storage: user + assistant messages saved together after completion,
  preventing dangling messages on abort
- GFM markdown: tables, strikethrough via remark-gfm plugin + table styles
- Performance: memo user messages and completed assistant messages, only
  re-render the active streaming message
- Model config: gpt-5.2, claude-opus-4.6 as chairman
- Always show input box for multi-turn conversations

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/frontend/src/components/ChatInterface.css b/frontend/src/components/ChatInterface.css
index 0d01300..63bc75d 100644
--- a/frontend/src/components/ChatInterface.css
+++ b/frontend/src/components/ChatInterface.css
@@ -161,3 +161,22 @@
   background: #ccc;
   border-color: #ccc;
 }
+
+.stop-button {
+  padding: 14px 28px;
+  background: #e24a4a;
+  border: 1px solid #e24a4a;
+  border-radius: 8px;
+  color: #fff;
+  font-size: 15px;
+  font-weight: 600;
+  cursor: pointer;
+  transition: background 0.2s;
+  white-space: nowrap;
+  align-self: flex-end;
+}
+
+.stop-button:hover {
+  background: #c93636;
+  border-color: #c93636;
+}