fix(documents): tighten owner resolution + cover company/yacht paths

Three follow-ups from Task 7 code review:
1. Drop the dead interest.yachtId fallback branch. interests.clientId
   is NOT NULL so the yacht branch was unreachable. Comment explains
   the schema constraint so the branch can be re-added if that
   constraint is ever relaxed.
2. Add defense-in-depth port_id filter to the interests lookup
   inside resolveDocumentOwner (matches CLAUDE.md convention and
   every other interests query in this file).
3. Add two integration test cases for direct-company and direct-yacht
   owner resolution — closes the coverage gap where the signed-file
   row's companyId/yachtId columns are populated for the first time
   in this commit chain.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/services/documents.service.ts

@@ -1079,27 +1079,30 @@ interface ResolvedOwner {
  * companyId (per schema), so the company branch is omitted from the
  * interest fallback. Returns null when no owner is resolvable.
  */
-async function resolveDocumentOwner(doc: {
-  clientId: string | null;
-  companyId: string | null;
-  yachtId: string | null;
-  interestId: string | null;
-}): Promise<ResolvedOwner | null> {
+async function resolveDocumentOwner(
+  portId: string,
+  doc: {
+    clientId: string | null;
+    companyId: string | null;
+    yachtId: string | null;
+    interestId: string | null;
+  },
+): Promise<ResolvedOwner | null> {
   if (doc.clientId) return { entityType: 'client', entityId: doc.clientId };
   if (doc.companyId) return { entityType: 'company', entityId: doc.companyId };
   if (doc.yachtId) return { entityType: 'yacht', entityId: doc.yachtId };
 
   if (doc.interestId) {
+    // interests.clientId is NOT NULL — if the interest row exists, the
+    // client owner is always resolvable through it. The yacht-only path
+    // would require relaxing the schema constraint first.
     const interest = await db.query.interests.findFirst({
-      where: eq(interests.id, doc.interestId),
-      columns: { clientId: true, yachtId: true },
+      where: and(eq(interests.id, doc.interestId), eq(interests.portId, portId)),
+      columns: { clientId: true },
     });
     if (interest?.clientId) {
       return { entityType: 'client', entityId: interest.clientId };
     }
-    if (interest?.yachtId) {
-      return { entityType: 'yacht', entityId: interest.yachtId };
-    }
   }
   return null;
 }
@@ -1129,12 +1132,17 @@ export async function handleDocumentCompleted(eventData: { documentId: string; p
 
     // Resolve owner via the Owner-wins chain. The signed PDF lands in
     // this owner's auto-created entity subfolder (or at root if no owner).
-    const owner = await resolveDocumentOwner(doc);
+    const owner = await resolveDocumentOwner(doc.portId, doc);
 
     let entityFolderId: string | null = null;
     if (owner) {
       try {
-        const folder = await ensureEntityFolder(doc.portId, owner.entityType, owner.entityId, 'system');
+        const folder = await ensureEntityFolder(
+          doc.portId,
+          owner.entityType,
+          owner.entityId,
+          'system',
+        );
         entityFolderId = folder.id;
       } catch (err) {
         // Folder creation is best-effort — signed file still lands at root.