Swap title icon from brain-EEG to chat-and-papers (#26)

The brain-with-EEG-electrodes icon framed Open Science Assistant as
a neuroscience-only tool. The platform serves seven communities
spanning data standards, annotation, BCI, and analysis, so a generic
'AI answering from research literature' icon reads more accurately.

New icon (ai-icon-title-a.png) shows a speech bubble above a stack
of papers with an emerald-green folded-corner accent, generated to
match the deck's existing two-color flat-line style.

Author: neuromechanist

docs/osa/presentations/slides/uc-open-2026/images/ai-icon-brain-eeg.png

@@ -33,8 +33,8 @@
         "elements": [
           {
             "type": "image",
-            "src": "./images/ai-icon-brain-eeg.png",
-            "alt": "Research community icon",
+            "src": "./images/ai-icon-title-a.png",
+            "alt": "Chat bubble above a stack of research papers, representing an AI assistant answering from community literature",
             "width": "130px",
             "position": { "area": "center", "order": 0 }
           },