Fix Portuguese coverage gaps: synonyms, translations, frequency, gerunds

- Extract sense-level synonyms/antonyms from Wiktionary (not just top-level),
  dramatically improving Portuguese synonym coverage
- Add bidirectional translation lookup so pt→en queries find en→pt entries
  stored by English Wiktionary loader, with reverse index for performance
- Fix frequency loader: auto-detect column order (count\tword vs word\tcount),
  auto-detect ISO-8859-1 encoding and convert to UTF-8, insert missing words
  instead of only updating existing ones
- Switch WordNet download from 3.1 to 3.0 to match WOLF/OMW synset offsets
- Add OpenSubtitles-derived Portuguese frequency list (hermitdave/FrequencyWords)
- Increase affix expansion cap from 30→80 forms per word for Portuguese gerunds

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

scripts/download-dict-data.sh

@@ -412,17 +412,21 @@ fi
 # pt-PT — CETEMPúblico frequency (or fallback frequency list)
 # ============================================================
 echo "=== Portuguese frequency data ==="
-PT_FREQ_FILE="$DATA_DIR/cetempublico-freq.tsv"
+PT_FREQ_FILE="$DATA_DIR/pt_50k.txt"
 if [[ -f "$PT_FREQ_FILE" && "$FORCE" != "true" ]]; then
-    echo "  [skip] cetempublico-freq.tsv already exists"
-elif [[ -f "$DATA_DIR/pt-freq.tsv" && "$FORCE" != "true" ]]; then
-    echo "  [skip] pt-freq.tsv already exists"
-else
-    echo "  [info] CETEMPúblico frequency data requires manual download from Linguateca."
-    echo "  Visit: https://www.linguateca.pt/acesso/corpus.php?corpus=CETEMPUBLICO"
-    echo "  Generate a word frequency list and save as: $PT_FREQ_FILE"
-    echo "  Format: word<TAB>frequency (one per line)"
-    echo "  The import will proceed without frequency data if this file is absent."
+    if check_min_size "$PT_FREQ_FILE" 100000; then
+        echo "  [skip] pt_50k.txt already exists (size ok)"
+    else
+        echo "  [warn] pt_50k.txt looks truncated, re-downloading"
+        rm -f "$PT_FREQ_FILE"
+    fi
+fi
+if [[ ! -f "$PT_FREQ_FILE" ]]; then
+    # OpenSubtitles-derived frequency list (hermitdave/FrequencyWords)
+    download "https://raw.githubusercontent.com/hermitdave/FrequencyWords/master/content/2016/pt/pt_50k.txt" "$PT_FREQ_FILE" 2>/dev/null || {
+        echo "  [warn] Portuguese frequency download failed."
+        echo "  The import will proceed without frequency data."
+    }
 fi
 
 # ============================================================