chore(changelog): add AI assistance mention to changelog

Add a mention next to the commit message when the commit is AI assisted
and group AI models used in an 'AI Assistance Repartition' section.

Assisted-by: Zed:gemini-3.1-pro

cliff.toml

@@ -25,8 +25,26 @@ body = """
         - {% if commit.scope %}*({{ commit.scope }})* {% endif %}\
             {% if commit.breaking %}[**breaking**] {% endif %}\
             {{ commit.message | upper_first }}\
+            {%- for footer in commit.footers -%}
+                {%- if footer.token == "Assisted-by" %} *(🤖 {{ footer.value | trim }})*{%- endif -%}
+            {%- endfor %}\
     {% endfor %}
-{% endfor %}\n
+{% endfor %}
+
+{%- set ai_models = [] -%}
+{%- for commit in commits -%}
+    {%- for footer in commit.footers -%}
+        {%- if footer.token == "Assisted-by" -%}
+            {%- set_global ai_models = ai_models | concat(with=footer) -%}
+        {%- endif -%}
+    {%- endfor -%}
+{%- endfor -%}
+{%- if ai_models | length > 0 %}
+    ### 🤖 AI Assistance Repartition
+    {%- for model, occurrences in ai_models | group_by(attribute="value") %}
+    - **{{ model | trim }}**: {{ occurrences | length }} commit{% if occurrences | length > 1 %}s{% endif %}
+    {%- endfor %}
+{% endif %}\n
 """
 # template for the changelog footer
 footer = """