fix(studio): improve chat context, thinking tags, streaming, and tool results

- Fix cleanThinkingTags to use proper regex instead of naive ReplaceAll
- Send conversation history (last 20 messages + summary) to AI instead of single message
- Store tool results alongside tool calls so history shows complete execution info
- Stream words instead of characters for smoother SSE rendering
- Add stop button to cancel in-progress AI requests (AbortController)
- Fix markdown rendering: add h2 support, use div for bullets
- Add i18n keys for cancel/stop (EN + FR)

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

web/src/api/client.js

@@ -52,7 +52,7 @@ const api = {
   saveTerminalSettings: (settings) => request('/terminal/settings', { method: 'PUT', body: JSON.stringify(settings) }),
   getChatHistory: () => request('/chat/history'),
   clearChat: () => request('/chat/clear', { method: 'POST' }),
-  sendChat: (message, stream = true, onChunk) => {
+  sendChat: (message, stream = true, onChunk, signal) => {
     if (!stream) {
       return request('/chat', { method: 'POST', body: JSON.stringify({ message, stream: false }) })
     }
@@ -61,6 +61,7 @@ const api = {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({ message, stream: true }),
+        signal,
       }).then(async (res) => {
         if (!res.ok) {
           const err = await res.json().catch(() => ({ error: res.statusText }))