feat(notes): attach selected Notes/Todos as Agent context (#6495)

* feat: add Notes and Todos as agent chat context

- Send selected Note/Todo IDs from the Notes UI
- Load selected notes with owner scoping in chat routes
- Format note content and checklist items for the model
- Inject selected notes as untrusted chat context
- Add a selected-context indicator beside Shell Access
- Keep selected context associated with the active chat session

* Improved selected notes context handling and discouragin redundant note lookup and permission requests

* Fix selected notes UI when switching chats

* fix(notes): harden selected context lifecycle and validation

---------

Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

routes/chat_helpers.py

@@ -1010,6 +1010,7 @@ async def build_chat_context(
     chat_processor,
     message: str,
     session_id: str,
+    selected_notes_context: str | None = None,
     preset_id=None,
     att_ids: list = None,
     use_web=None,
@@ -1182,6 +1183,23 @@ async def build_chat_context(
     if search_context and allow_tool_preprocessing and not casual_low_signal:
         preface.append(untrusted_context_message("prefetched search context", search_context))
 
+    # Inject selected notes as context
+    if selected_notes_context:
+        selected_notes_context = (
+            "The following selected notes and todos are reference context explicitly chosen "
+            "by the user. Use them directly when relevant to the user's request. Do not "
+            "ask for permission to use this context, and do not call note-management "
+            "tools just to retrieve the same notes; use those tools only for a requested "
+            "change or when this context is insufficient.\n\n"
+            + selected_notes_context
+        )
+        preface.append(
+            untrusted_context_message(
+                "Selected notes and todos",
+                selected_notes_context,
+            )
+        )
+
     # YouTube transcripts
     for transcript in preprocessed.youtube_transcripts:
         preface.append(untrusted_context_message("youtube transcript", transcript))