feat(generator): add -default-view to choose timeline or grid as site root

The chosen view is published at /, the other under /timeline/ or
/grid/. Page paths, pager links and the cross-links between the views
are derived from the setting. The directory named after the default
view is removed on build, since it can only be a leftover from before
a switch.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

main.go

@@ -20,15 +20,20 @@ func main() {
 	serifFamily := flag.String("serif-family", "Crimson Pro", "CSS font-family for the primary serif text")
 	mlFamily    := flag.String("ml-family", "Manjari", "CSS font-family for the alt-script (Malayalam) bio line")
 	pageSize    := flag.Int("page-size", 60, "photos per page on the timeline and grid views (timeline packs whole days, so pages vary slightly around this)")
+	defaultView := flag.String("default-view", viewTimeline, "view published at the site root: \"timeline\" or \"grid\"; the other one is published under /<name>/")
 	flag.Parse()
 
+	if *defaultView != viewTimeline && *defaultView != viewGrid {
+		log.Fatalf("-default-view must be %q or %q, got %q", viewTimeline, viewGrid, *defaultView)
+	}
+
 	for _, d := range []string{*contentDir, *outputDir} {
 		if err := os.MkdirAll(d, 0755); err != nil {
 			log.Fatalf("mkdir %s: %v", d, err)
 		}
 	}
 
-	g := NewGenerator(*contentDir, *outputDir, *baseURL, *author, *handle, *bio, *bioAlt, *fontsURL, *serifFamily, *mlFamily, *pageSize)
+	g := NewGenerator(*contentDir, *outputDir, *baseURL, *author, *handle, *bio, *bioAlt, *fontsURL, *serifFamily, *mlFamily, *pageSize, *defaultView)
 
 	if err := g.Build(); err != nil {
 		log.Printf("initial build: %v", err)