Add Phase 2+3 features: antonyms, backing, pronunciation, etymology, difficulty, affix expansion

New endpoints: /antonyms, /backing, /pronunciation, /etymology with difficulty
scoring on /random. Cross-language synset backing links French/Portuguese words
to English equivalents via WordNet 3.0 synset IDs (matching WOLF and OMW offsets).

New loaders: Hunspell affix expansion (fr, pt-PT), English programmatic inflector,
CMU Pronouncing Dictionary, SUBTLEX-US frequency, CETEMPúblico frequency,
Open Multilingual Wordnet (Portuguese), and SQL-based difficulty scoring.

Schema v2 adds tables: antonyms, synsets, word_synsets, pronunciations, etymology
with migration support for existing databases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/dictionary/bench_test.go

@@ -0,0 +1,151 @@
+package dictionary
+
+import (
+	"database/sql"
+	"fmt"
+	"testing"
+
+	_ "modernc.org/sqlite"
+)
+
+func setupBenchDB(b *testing.B) (*Dictionary, *sql.DB) {
+	b.Helper()
+	db, err := sql.Open("sqlite", ":memory:?_pragma=foreign_keys(on)")
+	if err != nil {
+		b.Fatal(err)
+	}
+	db.SetMaxOpenConns(1)
+	if err := BootstrapSchema(db); err != nil {
+		b.Fatal(err)
+	}
+
+	// Seed a realistic-ish dataset: 1000 words with definitions, synonyms, translations
+	exec := func(q string, args ...any) {
+		if _, err := db.Exec(q, args...); err != nil {
+			b.Fatalf("seed: %s: %v", q, err)
+		}
+	}
+
+	exec("INSERT INTO meta (key, value) VALUES ('schema_version', '1')")
+	exec("INSERT INTO meta (key, value) VALUES ('imported_at', '2025-01-01T00:00:00Z')")
+
+	poses := []string{"noun", "verb", "adjective", "adverb"}
+	langs := []string{"en", "fr", "pt-PT"}
+
+	for i := 1; i <= 1000; i++ {
+		lang := langs[i%len(langs)]
+		pos := poses[i%len(poses)]
+		word := fmt.Sprintf("word%04d", i)
+		exec("INSERT INTO words (id, word, lang, pos, frequency) VALUES (?, ?, ?, ?, ?)",
+			i, word, lang, pos, i%100)
+
+		// 2 definitions per word
+		exec("INSERT INTO definitions (word_id, pos, gloss, source, priority) VALUES (?, ?, ?, 'wordnet', 10)",
+			i, pos, fmt.Sprintf("definition A of %s", word))
+		exec("INSERT INTO definitions (word_id, pos, gloss, source, priority) VALUES (?, ?, ?, 'wiktionary', 20)",
+			i, pos, fmt.Sprintf("definition B of %s", word))
+
+		// 2 synonyms
+		exec("INSERT INTO synonyms (word_id, synonym, source) VALUES (?, ?, 'wordnet')",
+			i, fmt.Sprintf("syn1_%s", word))
+		exec("INSERT INTO synonyms (word_id, synonym, source) VALUES (?, ?, 'wordnet')",
+			i, fmt.Sprintf("syn2_%s", word))
+
+		// Translation for en words
+		if lang == "en" {
+			exec("INSERT INTO translations (word_id, translation, target_lang, source) VALUES (?, ?, 'fr', 'wiktionary')",
+				i, fmt.Sprintf("fr_%s", word))
+		}
+	}
+
+	return NewFromDB(db), db
+}
+
+func BenchmarkIsValidWord(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	b.Run("hit", func(b *testing.B) {
+		for b.Loop() {
+			d.IsValidWord("word0003", "en")
+		}
+	})
+	b.Run("miss", func(b *testing.B) {
+		for b.Loop() {
+			d.IsValidWord("nonexistent", "en")
+		}
+	})
+}
+
+func BenchmarkRandomWord(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	b.Run("no_filter", func(b *testing.B) {
+		for b.Loop() {
+			d.RandomWord("en", Options{})
+		}
+	})
+	b.Run("with_filters", func(b *testing.B) {
+		for b.Loop() {
+			d.RandomWord("en", Options{POS: "noun", MinLength: 4, MaxLength: 10})
+		}
+	})
+}
+
+func BenchmarkDefine(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	b.Run("with_defs", func(b *testing.B) {
+		for b.Loop() {
+			d.Define("word0003", "en")
+		}
+	})
+	b.Run("no_defs", func(b *testing.B) {
+		for b.Loop() {
+			d.Define("nonexistent", "en")
+		}
+	})
+}
+
+func BenchmarkSynonyms(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	b.Run("with_syns", func(b *testing.B) {
+		for b.Loop() {
+			d.Synonyms("word0003", "en")
+		}
+	})
+	b.Run("no_syns", func(b *testing.B) {
+		for b.Loop() {
+			d.Synonyms("nonexistent", "en")
+		}
+	})
+}
+
+func BenchmarkTranslate(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	b.Run("with_trans", func(b *testing.B) {
+		for b.Loop() {
+			d.Translate("word0003", "en", "fr")
+		}
+	})
+	b.Run("no_trans", func(b *testing.B) {
+		for b.Loop() {
+			d.Translate("nonexistent", "en", "fr")
+		}
+	})
+}
+
+func BenchmarkWordCount(b *testing.B) {
+	d, db := setupBenchDB(b)
+	defer db.Close()
+
+	for b.Loop() {
+		d.WordCount()
+	}
+}