Make Help > Help Topics show full command-line help, at least

README.md

@@ -134,7 +134,6 @@ cat samples/ship.ans
 - The selection box border appears inside instead of outside (and lacks dashes). For the text box, I hid the border because it was too visually confusing, but it should also have an outer border.
 - Pick Color can't be cancelled (with Esc or by pressing both mouse buttons), since it samples the color continuously.
 - Pressing both mouse buttons stops the current tool, but doesn't undo the current action.
-- Help > Help Topics isn't very helpful. I thought it would be funny to include the command line usage, but it doesn't even describe the options, unlike running with `--help`.
 - Due to limitations of the terminal, shortcuts using Shift or Alt might not work.
 - Menus are not keyboard navigable.
 - Clicking the Zoom submenu doesn't always work. You just have to click it a few times before it opens. <!--(It may be technically open but positioned off screen, or lacking width/height, or infinitely sized. I don't know. It seems to explode in size before disappearing.)-->

src/textual_paint/paint.css

@@ -237,10 +237,12 @@ CharacterSelectorDialogWindow .cancel {
 #help_dialog .window_content {
     padding: 2 4;
 }
-#help_dialog .help_text {
+#help_dialog .help_text_container {
     width: 80;
     height: auto;
-    overflow-y: auto;
+    max-height: 15;
+    overflow: auto;
+    margin-bottom: 2;
 }
 
 #zoom_dialog .window_content {

src/textual_paint/paint.py

@@ -2293,8 +2293,8 @@ class PaintApp(App[None]):
             title=_("Help"),  # _("Help Topics") not really apt yet since it's just the usage
             handle_button=lambda button: window.close(),
         )
-        help_text = parser.format_usage()
-        window.content.mount(Static(help_text,  classes="help_text"))
+        help_text = parser.format_help()
+        window.content.mount(Container(Static(help_text),  classes="help_text_container"))
         window.content.mount(Button(_("OK"), classes="ok submit"))
         self.mount(window)