Fix Manage Environments dialog scroll position and widen dialog

Reset horizontal scroll to leftmost position on open so variable names
are always visible first. Increase dialog width from 1100 to 1200px.

src/environments-dialog.ui

@@ -5,7 +5,7 @@
 
   <template class="EnvironmentsDialog" parent="AdwDialog">
     <property name="title">Manage Environments</property>
-    <property name="content-width">1100</property>
+    <property name="content-width">1200</property>
     <property name="content-height">600</property>
     <property name="follows-content-size">false</property>
 
@@ -18,7 +18,7 @@
         </child>
 
         <property name="content">
-          <object class="GtkScrolledWindow">
+          <object class="GtkScrolledWindow" id="scrolled_window">
             <property name="vexpand">true</property>
             <child>
               <object class="AdwClamp">

src/environments_dialog.py

@@ -34,6 +34,7 @@ class EnvironmentsDialog(Adw.Dialog):
 
     table_container = Gtk.Template.Child()
     add_environment_button = Gtk.Template.Child()
+    scrolled_window = Gtk.Template.Child()
 
     __gsignals__ = {
         'environments-updated': (GObject.SIGNAL_RUN_FIRST, None, ()),
@@ -48,6 +49,10 @@ class EnvironmentsDialog(Adw.Dialog):
         self.header_row = None
         self.data_rows = []
         self._populate_table()
+        self.connect('map', self._scroll_to_start)
+
+    def _scroll_to_start(self, widget):
+        self.scrolled_window.get_hadjustment().set_value(0)
 
     def _populate_table(self):
         """Populate the transposed environment-variable table."""