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_test.go

@@ -95,3 +95,27 @@ func TestLibraryTypeDisplayName(t *testing.T) {
 		}
 	}
 }
+
+func TestPrettifyGenre(t *testing.T) {
+	cases := []struct{ in, want string }{
+		{"science fiction", "Science Fiction"},
+		{"sword & sorcery", "Sword & Sorcery"},
+		{"action & adventure", "Action & Adventure"},
+		{"war & military", "War & Military"},
+		{"historical fiction", "Historical Fiction"},
+		{"children's", "Children's"},
+		{"middle grade", "Middle Grade"},
+		{"fiction", "Fiction"},
+		// Small words stay down except in first position.
+		{"towers of midnight", "Towers of Midnight"},
+		// Mixed case = user-authored; verbatim.
+		{"Science Fiction", "Science Fiction"},
+		{"HardSF", "HardSF"},
+		{"", ""},
+	}
+	for _, c := range cases {
+		if got := prettifyGenre(c.in); got != c.want {
+			t.Errorf("prettifyGenre(%q) = %q, want %q", c.in, got, c.want)
+		}
+	}
+}