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>

static/index.html

@@ -1178,6 +1178,21 @@
               <polyline points="4 17 10 11 4 5"/><line x1="12" y1="19" x2="20" y2="19"/>
             </svg>
           </button>
+          <!-- Selected Notes/Todos indicator -->
+          <button
+            type="button"
+            class="input-icon-btn tool-indicator"
+            title="Selected Notes/Todos context — click to clear"
+            id="selected-notes-context-btn"
+            aria-label="Clear selected Notes/Todos context"
+            style="display:none;"
+          >
+            <span id="selected-notes-context-count" style="font-size:11px;margin-left:2px;"></span>
+            <svg class="tool-indicator-x" width="10" height="10" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="3" stroke-linecap="round" aria-hidden="true">
+              <line x1="6" y1="6" x2="18" y2="18"/>
+              <line x1="18" y1="6" x2="6" y2="18"/>
+            </svg>
+          </button>
           <!-- Workspace indicator (hidden until a folder is set) -->
           <button type="button" class="input-icon-btn tool-indicator" title="Workspace - click to clear" id="workspace-indicator-btn" aria-label="Clear workspace" style="display:none;">
             <svg class="workspace-indicator-icon" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M3 7a2 2 0 0 1 2-2h4l2 2h8a2 2 0 0 1 2 2v8a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2z"/></svg>