Sprint 17: homograph example dedup + plural audio + prep extraction

- Homograph collision fix: _deduplicate_confusable_examples() clears
  shared examples from less-common confusable group members (36 entries
  fixed). Keeps examples only on highest-frequency meaning.
- Plural deck audio: wired up PluralAudio field in apkg_builder.py,
  downloaded 613 plural audio files from pealim.com for all deck entries.
- Prep extraction upstream: moved Hebrew preposition parsing from build
  time into list/detail scrapers (SCHEMA.yaml prep field added).
- Validation: new no_shared_confusable_examples check in validate_data.py
- Tests: 9 new unit tests for confusable deduplication (98 total)
- Release: v0.19

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

SCHEMA.yaml

@@ -27,6 +27,7 @@ entry:
   pos_hebrew: "שֵׁם עֶצֶם"          # Part of speech in Hebrew (with nikkud)
   meaning: "father"                # English meaning (cleaned — no inline emoji, no Hebrew prepositions)
   meaning_raw: "father 👨"         # Original meaning as scraped (may contain emoji and/or Hebrew preps)
+  prep: "על"                       # Hebrew preposition(s) governing this word, extracted from meaning_raw (e.g. "(על)" → "על"); null if none
   audio_url: "https://..."         # Pealim audio URL
   audio_file: "6009-av.mp3"        # Local filename (slug-based for confusables, consonant-based otherwise)
   tags: ""                         # Pealim tags if any

apkg_builder.py

@@ -35,7 +35,7 @@ COMPLETE_PLURAL_DECK_ID = 1_234_567_903
 
 # Release version tag added to all notes so users can identify which release
 # their cards come from (visible in Anki's Browse view and card info).
-RELEASE_TAG = "v0.18"
+RELEASE_TAG = "v0.19"
 
 # Regex for extracting emoji and Hebrew prepositions from meaning strings
 EMOJI_RE = re.compile(r"[\U0001F000-\U0001FFFF\u2600-\u27FF\u2300-\u23FF\uFE00-\uFE0F]+")
@@ -906,9 +906,14 @@ def build_vocab_deck(
                     emoji_str = emoji_lookup[kw]
                     break
 
-        # Extract Hebrew prepositions from meaning_raw
-        preps = HBPAREN_RE.findall(meaning_raw)
-        prep_str = " ".join(f"({p})" for p in preps)
+        # Extract Hebrew prepositions: prefer upstream-parsed prep field, fall back to meaning_raw scan
+        # (fallback covers entries scraped before prep was moved upstream)
+        entry_prep = entry.get("prep")
+        if entry_prep:
+            prep_str = " ".join(f"({p})" for p in entry_prep.split())
+        else:
+            preps = HBPAREN_RE.findall(meaning_raw)
+            prep_str = " ".join(f"({p})" for p in preps)
 
         # Audio — use audio_file from entry; for confusables it's already slug-based