fix(persistence): skip upsert_page archive when source_hash is unchanged

Previously upsert_page always archived the existing PageVersion and
incremented the version counter, even when the source file had not changed.
Now it returns early if existing.source_hash == source_hash, avoiding
unnecessary PageVersion rows and redundant writes during Phase 4 batch
persist after incremental per-page saves in Phase 3.

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

Author: dmikushin

packages/core/src/repowise/core/persistence/crud.py

@@ -239,6 +239,10 @@ async def upsert_page(
     existing = existing_result.scalar_one_or_none()
 
     if existing is not None:
+        # Skip update if source content has not changed
+        if existing.source_hash == source_hash:
+            return existing
+
         # Archive the current state before overwriting
         snapshot = PageVersion(
             id=_new_uuid(),