feat: make resolve endpoint non-blocking, documentation optional

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/endpoints/ai_sessions.py

@@ -420,7 +420,7 @@ async def resolve_session(
     db: Annotated[AsyncSession, Depends(get_db)],
     _: None = Depends(require_engineer_or_admin),
 ):
-    """Resolve a FlowPilot session and generate documentation."""
+    """Resolve a session. Returns immediately; use /documentation/stream for ticket notes."""
     try:
         result = await flowpilot_engine.resolve_session(
             session_id=session_id,
@@ -433,16 +433,21 @@ async def resolve_session(
     except PermissionError as e:
         raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail=str(e))
 
-    # Generate resolution outputs (branching feature)
-    try:
-        from app.services.resolution_output_generator import ResolutionOutputGenerator
-        gen = ResolutionOutputGenerator(db)
-        await gen.generate_all(session_id)
-    except Exception:
-        logger.exception(f"Failed to generate resolution outputs for session {session_id}")
-        # Non-blocking — resolve still succeeds even if output generation fails
-
     await db.commit()
+
+    # Fire-and-forget: resolution outputs (don't block the response)
+    import asyncio
+
+    async def _post_resolve_tasks():
+        try:
+            from app.services.resolution_output_generator import ResolutionOutputGenerator
+            gen = ResolutionOutputGenerator(db)
+            await gen.generate_all(session_id)
+        except Exception:
+            logger.exception(f"Failed to generate resolution outputs for session {session_id}")
+
+    asyncio.create_task(_post_resolve_tasks())
+
     return result