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/loader/omw.go

@@ -0,0 +1,159 @@
+package loader
+
+import (
+	"bufio"
+	"database/sql"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// OMWLoader loads Open Multilingual Wordnet data for Portuguese,
+// mapping pt-PT words to Princeton WordNet synset IDs.
+type OMWLoader struct{}
+
+func (OMWLoader) Name() string { return "omw-pt" }
+
+func (OMWLoader) Load(db *sql.DB, dataDir string) error {
+	// OMW Portuguese data comes as a tab-separated file.
+	// Format varies by release but typically:
+	//   synset_id<tab>relation<tab>word
+	// where synset_id is like "eng-30-00001740-n" and relation is "lemma"
+	//
+	// Also supports the WN-LMF XML format and the simpler tab format from
+	// https://github.com/omwn/omw-data
+
+	// Try multiple possible file locations
+	candidates := []string{
+		filepath.Join(dataDir, "omw", "wn-data-por.tab"),
+		filepath.Join(dataDir, "omw", "wn-por.tab"),
+		filepath.Join(dataDir, "omw-pt.tab"),
+	}
+
+	var path string
+	for _, c := range candidates {
+		if _, err := os.Stat(c); err == nil {
+			path = c
+			break
+		}
+	}
+	if path == "" {
+		slog.Warn("omw-pt: no data file found, skipping", "searched", candidates)
+		return nil
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		return fmt.Errorf("omw: begin tx: %w", err)
+	}
+	defer tx.Rollback()
+
+	stmtSynset, err := tx.Prepare(`
+		INSERT OR IGNORE INTO synsets (synset_id, pos) VALUES (?, ?)`)
+	if err != nil {
+		return fmt.Errorf("omw: prepare synset: %w", err)
+	}
+	defer stmtSynset.Close()
+
+	stmtWordSynset, err := tx.Prepare(`
+		INSERT OR IGNORE INTO word_synsets (word_id, synset_id, source)
+		SELECT w.id, s.id, 'omw'
+		FROM words w, synsets s
+		WHERE w.word = ? AND w.lang = 'pt-PT' AND s.synset_id = ?`)
+	if err != nil {
+		return fmt.Errorf("omw: prepare word_synset: %w", err)
+	}
+	defer stmtWordSynset.Close()
+
+	f, err := os.Open(path)
+	if err != nil {
+		return fmt.Errorf("omw: open: %w", err)
+	}
+	defer f.Close()
+
+	posMap := map[string]string{
+		"n": "noun",
+		"v": "verb",
+		"a": "adjective",
+		"r": "adverb",
+	}
+
+	scanner := bufio.NewScanner(f)
+	var synsetCount, linkCount int
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "#") || line == "" {
+			continue
+		}
+
+		fields := strings.Split(line, "\t")
+		if len(fields) < 3 {
+			continue
+		}
+
+		synsetRaw := fields[0]
+		relation := fields[1]
+		word := strings.ToLower(strings.TrimSpace(fields[2]))
+
+		// Only process lemma relations
+		if relation != "lemma" {
+			continue
+		}
+
+		if word == "" || containsDigit(word) || containsSpace(word) {
+			continue
+		}
+
+		// Normalize synset ID: "eng-30-00001740-n" -> "00001740-n"
+		synsetID := normalizeOMWSynsetID(synsetRaw)
+		if synsetID == "" {
+			continue
+		}
+
+		// Extract POS from synset ID
+		parts := strings.Split(synsetID, "-")
+		if len(parts) != 2 {
+			continue
+		}
+		pos := posMap[parts[1]]
+		if pos == "" {
+			continue
+		}
+
+		if _, err := stmtSynset.Exec(synsetID, pos); err != nil {
+			return fmt.Errorf("omw: insert synset: %w", err)
+		}
+		synsetCount++
+
+		if _, err := stmtWordSynset.Exec(word, synsetID); err != nil {
+			return fmt.Errorf("omw: insert word_synset: %w", err)
+		}
+		linkCount++
+	}
+
+	if err := scanner.Err(); err != nil {
+		return fmt.Errorf("omw: scan: %w", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("omw: commit: %w", err)
+	}
+	slog.Info("omw-pt loaded", "synsets", synsetCount, "links", linkCount)
+	return nil
+}
+
+func normalizeOMWSynsetID(raw string) string {
+	// Format: "eng-30-00001740-n" -> "00001740-n"
+	parts := strings.Split(raw, "-")
+	if len(parts) >= 4 && parts[0] == "eng" {
+		return parts[2] + "-" + parts[3]
+	}
+	// Already normalized
+	if len(parts) == 2 && len(parts[0]) == 8 {
+		return raw
+	}
+	return ""
+}