feat(facets): facet registry, Batch A server params, genre model v2, facets endpoint

Phase 1 + backend of Phase 2 of the faceted-navigation plan. One
declarative facet registry (services/facet_registry.go) drives the
bookshelf filter system; a drift-guard unit test reflects over the
generated SearchMediaItemsUnifiedParams so a registry entry and its
sqlc.narg block can never disagree silently.

- Nine new filter params on SearchMediaItemsUnified: story_arc,
  imprint, edition (scalar-fuzzy), age_rating, format_group,
  manga_type, reading_direction (exact), explicit, abridged
  (presence-bound bools). Comma = OR-within multi-select on every
  text facet; AND-across-facets unchanged.
- Genre model v2 (user rule: a subgenre is not a genre, it's a tag):
  genre_lexicon.go rebuilt as shelf set + subgenre->shelf map;
  pickSmartGenre picks direct shelf > mapped subgenre > Fiction floor
  > empty (unknown-only stays tags-only). Type-words (Manga, Comics,
  Graphic Novel) join the demote list. Both 'adventure' and 'action &
  adventure' are shelves — provider data uses both and the verified
  traces pin them.
- Language filter UX: comma elements normalize through the ingest
  language map, so display names ('English') match rows stored as ISO
  codes ('en'). The language autocomplete now serves display names.
- NEW GET /api/media-items/facets?facet=X&library_id=... — registry-
  driven value+count listing (14 static per-column queries, family-lens
  join); language values carry display names; bool/range facets 400.
- Family-lens gates: an explicit hidden-library library_id is now a
  403 on the search endpoints (was a silent empty set) — JSON branch
  and HTMX grid partial both.
- handlers.ParseMediaSearchParams is the SINGLE param parser for the
  search JSON endpoint and the HTMX grid partial; the HTML branch
  previously dropped publisher_filter and narrator_filter silently.

Pins: docs/contract_pins.md changelog entries (additive request
params; new facets endpoint). Tests: facet_registry_test.go (shape +
SQL drift guard + library-type union), series_parsing_test.go genre-v2
cases, facets_integration_test.go (param filtering e2e, counts,
language display, 403s) — container runner.

internal/services/series_parsing_test.go

@@ -26,10 +26,10 @@ func TestSplitSeriesString(t *testing.T) {
 
 func TestSeriesSequenceNumber(t *testing.T) {
 	cases := []struct {
-		in        string
-		num       float64
-		found     bool
-		lossy     bool
+		in    string
+		num   float64
+		found bool
+		lossy bool
 	}{
 		{"3", 3, true, false},
 		{"1.5", 1.5, true, false},
@@ -181,12 +181,34 @@ func TestPickSmartGenre(t *testing.T) {
 	if genre, _ := pickSmartGenre([]string{"Audiobook"}); genre != "" {
 		t.Errorf("audiobook is not a genre, got %q", genre)
 	}
-	// Fiction is the last resort, not the winner.
+	// Fiction is the floor: alone it resolves, against a real shelf it loses.
 	if genre, _ := pickSmartGenre([]string{"Fiction"}); genre != "fiction" {
 		t.Errorf("plain Fiction should still resolve, got %q", genre)
 	}
-	if genre, _ := pickSmartGenre([]string{"Fiction", "Epic Fantasy"}); genre != "epic fantasy" {
-		t.Errorf("specificity must beat generic, got %q", genre)
+	// Genre model v2: Epic Fantasy is a SUBGENRE — the genre column gets
+	// its parent shelf and the specific label lives in tags. (Intended
+	// change from the old longest-match behavior, which returned
+	// "epic fantasy" here.)
+	if genre, _ := pickSmartGenre([]string{"Fiction", "Epic Fantasy"}); genre != "fantasy" {
+		t.Errorf("subgenre must resolve to its shelf, got %q", genre)
+	}
+	// User-verified traces (Batch B decision):
+	if genre, _ := pickSmartGenre([]string{"Pirates", "Adventure"}); genre != "adventure" {
+		t.Errorf("direct shelf beats mapped subgenre, got %q", genre)
+	}
+	if genre, _ := pickSmartGenre([]string{"Pirates"}); genre != "adventure" {
+		t.Errorf("mapped subgenre alone resolves to its shelf, got %q", genre)
+	}
+	if genre, _ := pickSmartGenre([]string{"Sci-Fi", "Science Fiction", "Fiction"}); genre != "science fiction" {
+		t.Errorf("direct shelf beats floor, got %q", genre)
+	}
+	// Type-words describe the library type, not a shelf.
+	if genre, _ := pickSmartGenre([]string{"Manga"}); genre != "" {
+		t.Errorf("manga is a type-word, got %q", genre)
+	}
+	// Unknown-only input: no shelf is known — tags carry it, never guess.
+	if genre, all := pickSmartGenre([]string{"Completely Made-Up Genre"}); genre != "" {
+		t.Errorf("unknown-only input must leave genre empty, got %q (tags=%v)", genre, all)
 	}
 }