refactor: remove dead partial-render guard in resync_manga

The first guard block computed the partial-render condition but had an empty
if-body, so it never skipped anything — the real skip is the chapter-sync
guard further down. Delete the dead block and move its observability warning
into the live guard's else branch, eliminating the data-loss trap without
changing behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/crawler/resync.rs

@@ -135,28 +135,7 @@ impl ResyncService for RealResyncService {
             .await
             .with_context(|| format!("fetch_manga during resync of {manga_id}"))?;
 
-        // Partial-render guard: same logic as run_metadata_pass.
         let source_id = source.id();
-        if !manga.chapters.is_empty() || {
-            let prior = repo::crawler::live_chapter_count_for_source_manga(
-                &self.db,
-                source_id,
-                &source_manga_key,
-            )
-            .await
-            .unwrap_or(0);
-            prior == 0
-        } {
-            // Either the new fetch surfaced chapters, or there were
-            // none before either — chapter sync is safe to run.
-        } else {
-            tracing::warn!(
-                %manga_id,
-                source_url = %source_url,
-                "resync_manga: fetch returned empty chapters but prior count > 0; skipping chapter sync to avoid soft-drop"
-            );
-        }
-
         let upsert = repo::crawler::upsert_manga_from_source(
             &self.db,
             source_id,
@@ -201,6 +180,11 @@ impl ResyncService for RealResyncService {
         )
         .await
         .unwrap_or(0);
+        // Partial-render guard (same logic as run_metadata_pass): only sync
+        // chapters when the fetch surfaced some, or the manga never had any.
+        // A fetch that returned empty while a prior count exists is almost
+        // certainly a partial render — skip the sync so we don't soft-drop the
+        // real chapters.
         if !manga.chapters.is_empty() || prior_chapter_count == 0 {
             match repo::crawler::sync_manga_chapters(
                 &self.db,
@@ -223,6 +207,12 @@ impl ResyncService for RealResyncService {
                     "resync_manga: chapter sync failed"
                 ),
             }
+        } else {
+            tracing::warn!(
+                %manga_id,
+                source_url = %source_url,
+                "resync_manga: fetch returned empty chapters but prior count > 0; skipping chapter sync to avoid soft-drop"
+            );
         }
 
         drop(lease);