fix: filter Open WebUI background task requests from intent classifier

Open WebUI sends 4-5 extra requests per chat: query augmentation (Query: ...),
title generation, tag generation, and follow-up question suggestions. These all
include the full chat history, so they match execute/task intents incorrectly.

Added early return to classify_intent for Open WebUI system prompt patterns.

app/intent.py

@@ -61,6 +61,18 @@ def classify_intent(message: str) -> str:
     msg = message.lower()
     words = set(msg.split())
 
+    # Open WebUI background tasks — sent automatically after every chat response.
+    # They include the full chat history, so they'd mis-trigger execute/task intents.
+    # Patterns: "### Task:", "Query: <text>" (query augmentation), meta-task keywords.
+    if (msg.startswith("### task:") or
+            msg.startswith("query:") or
+            "chat history" in msg or
+            "summarizing the chat" in msg or
+            "categorizing the main themes" in msg or
+            "follow-up questions" in msg or
+            "3-5 word title" in msg):
+        return "planning"
+
     # Project creation — check before task/query
     if any(p in msg for p in CREATE_PROJECT_PHRASES):
         return "create_project"