Draw the commit graph in the demos with the detailed style

The 'auto' style doesn't recognize the terminal that vhs records, so it
would draw the classic graph. Now that the recordings have a font for
the branch drawing symbols, use the detailed graph in all demos.

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

pkg/integration/tests/demo/shared.go

@@ -16,4 +16,7 @@ func setGeneratedAuthorColours(config *config.AppConfig) {
 func setDefaultDemoConfig(config *config.AppConfig) {
 	// demos look much nicer with icons shown
 	config.GetUserConfig().Gui.NerdFontsVersion = "3"
+	// The terminal that we record demos in doesn't tell us that it can draw the
+	// detailed graph; demo/settings.tape gives it a font for it
+	config.GetUserConfig().Gui.CommitGraphStyle = "detailed"
 }