fix(sync-engine): merge title from getDocument and skip unchanged docs after hydration

- Merge title from getDocument during deferred hydration so Gmail
  documents get the email Subject header instead of the snippet text
- After hydration, compare the hydrated contentHash against the stored
  DB hash — if they match, skip the update. This prevents Obsidian
  (and any connector with a force-refresh stub hash) from re-uploading
  and re-processing unchanged documents every sync

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

Author: waleedlatif1

apps/sim/lib/knowledge/connectors/sync-engine.ts

@@ -456,12 +456,21 @@ export async function executeSync(
               syncContext
             )
             if (!fullDoc?.content.trim()) return null
+            const hydratedHash = fullDoc.contentHash ?? op.extDoc.contentHash
+            if (
+              op.type === 'update' &&
+              existingByExternalId.get(op.extDoc.externalId)?.contentHash === hydratedHash
+            ) {
+              result.docsUnchanged++
+              return null
+            }
             return {
               ...op,
               extDoc: {
                 ...op.extDoc,
+                title: fullDoc.title || op.extDoc.title,
                 content: fullDoc.content,
-                contentHash: fullDoc.contentHash ?? op.extDoc.contentHash,
+                contentHash: hydratedHash,
                 contentDeferred: false,
                 metadata: { ...op.extDoc.metadata, ...fullDoc.metadata },
               },