feat(facets+ui): clickable facet values everywhere, genre prettify, active-filter chips

Frontend half of the faceted-navigation Phase 2. 'Everything filterable
should be clickable': every displayed facet value links to the bookshelf
pre-filtered by its raw stored value; display forms are prettified at
render, never in the DB.

- templates/facet_links.templ: FacetLink (inline links) + FacetBadge
  (badge links) to /bookshelf?<facet>_filter=<value>; the raw value
  rides the param while the shown text is prettified, so matching and
  display can never disagree. Series/tags keep their dedicated pages
  by design; the card media-type icon stays unlinked (a derived kind,
  not a column value — deep-linking it would send wrong values).
- book_detail.templ: publisher, language, edition, genre, imprint
  cells + narrators line + age-rating/story-arc badges are now links.
- prettifyGenre (templates/utils.go + unit tests): title-cases only
  entirely-lowercase values; small words stay down except first
  position; & preserved. TS port for chip labels documents the twin.
- bookshelf.templ + bookshelf.ts: active-filter chips bar — Alpine
  renders chips from client-local form state (sanctioned island);
  one bubbled htmx:afterRequest hook keeps chips + shareable URL in
  sync; removeFilterChip clears the facet and re-applies. URL deep
  links now accept all 18 facet params (hidden inputs where the
  drawer has no field).

Pins changelog: Batch B/C entry in docs/contract_pins.md. Rendering
ownership guard (make lint-rendering) green.

templates/utils.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"sort"
 	"strings"
+	"unicode"
 	"time"
 
 	"github.com/google/uuid"
@@ -255,6 +256,41 @@ func conflictID(c *handlers.ConflictDetailResponse) string {
 	return c.ID
 }
 
+// genreSmallWords stay lowercase in title-case rendering (except the
+// first word of the value).
+var genreSmallWords = map[string]bool{
+	"a": true, "an": true, "and": true, "of": true, "the": true,
+	"in": true, "on": true, "for": true, "to": true, "or": true,
+}
+
+// prettifyGenre renders the canonically-lowercase genre value in title
+// case at display time (Batch B transform — never in the DB). Only
+// values that are ENTIRELY lowercase get transformed; anything else is
+// returned verbatim, protecting user-entered mixed case. Small words
+// stay down except in the first position; "&" has no case and passes
+// through. "science fiction" → "Science Fiction", "sword & sorcery" →
+// "Sword & Sorcery".
+func prettifyGenre(value string) string {
+	trimmed := strings.TrimSpace(value)
+	if trimmed == "" {
+		return ""
+	}
+	if trimmed != strings.ToLower(trimmed) {
+		return trimmed // mixed case = user-authored; display as written
+	}
+	words := strings.Fields(trimmed)
+	out := make([]string, len(words))
+	for i, w := range words {
+		if i > 0 && genreSmallWords[w] {
+			out[i] = w
+			continue
+		}
+		runes := []rune(w)
+		out[i] = string(append([]rune{unicode.ToUpper(runes[0])}, runes[1:]...))
+	}
+	return strings.Join(out, " ")
+}
+
 // getAlternateSeries extracts the alternate series name from JSONB data
 func getAlternateSeries(data []byte) string {
 	if len(data) == 0 {