slides: fix title page spacing, enable LIP6 and Sorbonne

- Reserve a left margin in the partner logo grid so a full grid stays
  clear of the affiliations.
- Let the space above the title shrink when the title page overflows,
  so the logos keep a bottom margin equal to the side margins.
- Enable the LIP6 and Sorbonne Université partners in the example deck.
- Note that author and institute blocks must stay plain: table and
  flushleft wrappers add vertical space.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Slides/slides-partners.sty

@@ -88,7 +88,8 @@
   {
     \int_set:Nn \l__slides_partner_count_int
       { \seq_count:N \l__slides_partner_files_seq }
-    \dim_set:Nn \l__slides_partner_width_dim {\linewidth}
+    % Keep a margin on the left so a full grid stays clear of the affiliations.
+    \dim_set:Nn \l__slides_partner_width_dim {.82\linewidth}
     \dim_set:Nn \l__slides_partner_maxheight_dim {.24\paperheight}
     \dim_set:Nn \l__slides_partner_xgap_dim
       { \fp_to_dim:n {min(.04 * \dim_to_fp:n {\linewidth},
@@ -153,7 +154,7 @@
               {
                 \int_compare:nNnT {##1} > {1}
                   { \vskip \l__slides_partner_ygap_dim }
-                \hbox_to_wd:nn {\l__slides_partner_width_dim}
+                \hbox_to_wd:nn {\linewidth}
                   {
                     \hfil
                     \int_step_inline:nnn {##1}

Slides/slides.cls

@@ -195,8 +195,10 @@
 \setbeamertemplate{title page}{
   % Use the theme's margins rather than a full-paper-height box, which placed
   % the footer almost on the page edge. Stretch only the space above the footer.
+  % If the content is too tall, shrink the top space so the footer keeps its
+  % bottom margin and the title moves up instead.
   \begin{minipage}[t][\dimexpr\paperheight-2\beamer@leftmargin\relax][s]{\textwidth}
-    \vspace*{.04\paperheight}
+    \vspace*{\dimexpr .04\paperheight\relax minus 1fill}
     \ifx\inserttitle\@empty\else\usebeamertemplate*{title}\fi
     \ifx\insertsubtitle\@empty\else\usebeamertemplate*{subtitle}\fi
     \vspace{.2cm}
@@ -210,7 +212,7 @@
         \column{0.44\linewidth}
         \insertpartnerlogos
     \end{columns}
-    \vspace*{.02\paperheight}
+    \vspace*{0pt}
   \end{minipage}
 }
 \makeatother

Slides/slides.tex

@@ -10,14 +10,17 @@
 \partner{ubo}
 \partner{ensta}
 % \partner{ifremer}
-% \partner{lip6}
+\partner{lip6}
-% \partner{sorbonne}
+\partner{sorbonne}
 % \partner{academia-sinica}
 % \partner{taipei}
 % See README.md for supported formats and custom logo paths.
 % Optional legacy title graphic (used only when no partners are enabled):
 % \titlegraphic{\flushright\includegraphics[height=1.3cm]{img/logos.png}\vspace{.5cm}}
 
+% Keep author and institute blocks plain: table or flushleft wrappers add
+% vertical space, which pushes the title up and misaligns the affiliations
+% with the partner logos.
 \author{
     \texorpdfstring{
         \begin{tabular}{@{}l@{}}