fix(cursor-chat): stabilize first-run UX and clean cursor message rendering

Fix three Cursor chat regressions observed on first message runs:

1. Full-screen UI refresh/flicker after first response.
2. Internal wrapper tags rendered in user messages.
3. Duplicate assistant message on response finalization.

Root causes
- Project refresh from chat completion used the global loading path,
  toggling app-level loading UI.
- Cursor history conversion rendered raw internal wrapper payloads
  as user-visible message text.
- Cursor response handling could finalize through overlapping stream/
  result paths, and stdout chunk parsing could split JSON lines.

Changes
- Added non-blocking project refresh plumbing for chat/session flows.
- Introduced fetch options in useProjectsState (showLoadingState flag).
- Added refreshProjectsSilently() to update metadata without global loading UI.
- Wired window.refreshProjects to refreshProjectsSilently in AppContent.

- Added Cursor user-message sanitization during history conversion.
- Added extractCursorUserQuery() to keep only <user_query> payload.
- Added sanitizeCursorUserMessageText() to strip internal wrappers:
  <user_info>, <agent_skills>, <available_skills>,
  <environment_context>, <environment_info>.
- Applied sanitization only for role === 'user' in
  convertCursorSessionMessages().

- Hardened Cursor backend stream parsing and finalization.
- Added line-buffered stdout parser for chunk-split JSON payloads.
- Flushed trailing unterminated stdout line on process close.
- Removed redundant content_block_stop emission on Cursor result.

- Added frontend duplicate guard in cursor-result handling.
- Skips a second assistant bubble when final result text equals
  already-rendered streamed content.

Code comments
- Added focused comments describing silent refresh behavior,
  tag stripping rationale, duplicate guard behavior, and line buffering.

Validation
- ESLint passes for touched files.
- Production build succeeds.

Files
- server/cursor-cli.js
- src/components/app/AppContent.tsx
- src/components/chat/hooks/useChatRealtimeHandlers.ts
- src/components/chat/utils/messageTransforms.ts
- src/hooks/useProjectsState.ts

src/components/chat/hooks/useChatRealtimeHandlers.ts

@@ -692,14 +692,28 @@ export function useChatRealtimeHandlers({
             const updated = [...previous];
             const lastIndex = updated.length - 1;
             const last = updated[lastIndex];
+            const normalizedTextResult = textResult.trim();
+
             if (last && last.type === 'assistant' && !last.isToolUse && last.isStreaming) {
               const finalContent =
-                textResult && textResult.trim()
+                normalizedTextResult
                   ? textResult
                   : `${last.content || ''}${pendingChunk || ''}`;
               // Clone the message instead of mutating in place so React can reliably detect state updates.
               updated[lastIndex] = { ...last, content: finalContent, isStreaming: false };
-            } else if (textResult && textResult.trim()) {
+            } else if (normalizedTextResult) {
+              const lastAssistantText =
+                last && last.type === 'assistant' && !last.isToolUse
+                  ? String(last.content || '').trim()
+                  : '';
+
+              // Cursor can emit the same final text through both streaming and result payloads.
+              // Skip adding a second assistant bubble when the final text is unchanged.
+              const isDuplicateFinalText = lastAssistantText === normalizedTextResult;
+              if (isDuplicateFinalText) {
+                return updated;
+              }
+
               updated.push({
                 type: resultData.is_error ? 'error' : 'assistant',
                 content: textResult,