fix(tau): introduce maximal tab length
Ellipsize titles longer then 24 character in the middle.
Horizontally expand tab labels to keep close buttons on the right side.
fixes
<object class="GtkLabel" id="tab_label">
<property name="visible">True</property>
<property name="can_focus">False</property>
+ <property name="hexpand">True</property>
</object>
<packing>
<property name="expand">False</property>
