feat(workers): sync.source_doc with sha256 diff

Fetches upstream URL via safe_fetch, sha256-diffs against the prior
body_sha stored in metadata, updates body_text + last_synced only when
content changed. Unchanged syncs just touch last_synced.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workers/void_workers/handlers/sourcedoc.py

@@ -0,0 +1,32 @@
+import hashlib
+from datetime import datetime, timezone
+from .. import repo
+from ..safe_fetch import safe_fetch
+
+NAME = "sync.source_doc"
+
+
+def _sha(data):
+    return hashlib.sha256(data).hexdigest()
+
+
+def handle(job_data: dict) -> dict:
+    sd_id = job_data["source_doc_id"]
+    doc = repo.get_source_doc(sd_id)
+    if not doc:
+        return {"skipped": "gone"}
+    body = safe_fetch(doc["upstream_url"], headers={"User-Agent": "void-ingest/2.0"})
+    new_sha = _sha(body)
+    old_sha = ((doc.get("metadata") or {}).get("body_sha"))
+    now = datetime.now(timezone.utc)
+    if new_sha == old_sha:
+        repo.update_source_doc(sd_id, last_synced=now)
+        return {"unchanged": True}
+    text = body.decode("utf-8", errors="replace")[:1_000_000]
+    repo.update_source_doc(
+        sd_id,
+        body_text=text,
+        last_synced=now,
+        metadata_patch={"body_sha": new_sha}
+    )
+    return {"updated": True, "chars": len(text)}