Fix remaining fuzzer issues: leaks and macOS SDK headers

sqlite-vec.c:
- vec0_free: add loops to free partition, auxiliary, and metadata
  column names (previously leaked on error paths)
- vec0_init: update pNew->numXxxColumns incrementally in the parse
  loop so vec0_free sees correct counts on early goto-error paths
  (previously the counts were only written after the loop, so vec0_free
  would loop 0 times and leak names allocated inside the loop)

fuzz.yaml:
- macOS: pass -isysroot $(xcrun --sdk macosx --show-sdk-path) so
  Xcode clang can find system headers (stdio.h, assert.h, etc.)
- Fix artifact upload paths: libFuzzer writes crash-*/leak-* to
  the cwd (repo root), not tests/fuzz/

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

.github/workflows/fuzz.yaml

@@ -55,9 +55,9 @@ jobs:
         with:
           name: fuzz-crashes-linux
           path: |
-            tests/fuzz/crash-*
-            tests/fuzz/leak-*
-            tests/fuzz/timeout-*
+            crash-*
+            leak-*
+            timeout-*
 
   fuzz-macos:
     runs-on: macos-14
@@ -70,9 +70,10 @@ jobs:
         run: make sqlite-vec.h
       - name: Build fuzz targets
         run: |
+          SDK=$(xcrun --sdk macosx --show-sdk-path)
           make -C tests/fuzz all \
             FUZZ_CC=$(xcrun -f clang) \
-            FUZZ_LDFLAGS=""
+            FUZZ_LDFLAGS="-isysroot $SDK"
       - name: Run fuzz targets
         run: |
           DURATION=${{ github.event.inputs.duration || '60' }}
@@ -100,9 +101,9 @@ jobs:
         with:
           name: fuzz-crashes-macos
           path: |
-            tests/fuzz/crash-*
-            tests/fuzz/leak-*
-            tests/fuzz/timeout-*
+            crash-*
+            leak-*
+            timeout-*
 
   fuzz-windows:
     # Best-effort: libFuzzer works on Windows via LLVM but ASAN/UBSAN

sqlite-vec.c

@@ -3659,6 +3659,21 @@ void vec0_free(vec0_vtab *p) {
     sqlite3_free(p->vector_columns[i].name);
     p->vector_columns[i].name = NULL;
   }
+
+  for (int i = 0; i < p->numPartitionColumns; i++) {
+    sqlite3_free(p->paritition_columns[i].name);
+    p->paritition_columns[i].name = NULL;
+  }
+
+  for (int i = 0; i < p->numAuxiliaryColumns; i++) {
+    sqlite3_free(p->auxiliary_columns[i].name);
+    p->auxiliary_columns[i].name = NULL;
+  }
+
+  for (int i = 0; i < p->numMetadataColumns; i++) {
+    sqlite3_free(p->metadata_columns[i].name);
+    p->metadata_columns[i].name = NULL;
+  }
 }
 
 int vec0_num_defined_user_columns(vec0_vtab *p) {
@@ -4742,6 +4757,7 @@ static int vec0_init(sqlite3 *db, void *pAux, int argc, const char *const *argv,
       pNew->user_column_idxs[user_column_idx] = numVectorColumns;
       memcpy(&pNew->vector_columns[numVectorColumns], &vecColumn, sizeof(vecColumn));
       numVectorColumns++;
+      pNew->numVectorColumns = numVectorColumns;
       user_column_idx++;
 
       continue;
@@ -4770,6 +4786,7 @@ static int vec0_init(sqlite3 *db, void *pAux, int argc, const char *const *argv,
       pNew->user_column_idxs[user_column_idx] = numPartitionColumns;
       memcpy(&pNew->paritition_columns[numPartitionColumns], &partitionColumn, sizeof(partitionColumn));
       numPartitionColumns++;
+      pNew->numPartitionColumns = numPartitionColumns;
       user_column_idx++;
       continue;
     }
@@ -4815,6 +4832,7 @@ static int vec0_init(sqlite3 *db, void *pAux, int argc, const char *const *argv,
       pNew->user_column_idxs[user_column_idx] = numAuxiliaryColumns;
       memcpy(&pNew->auxiliary_columns[numAuxiliaryColumns], &auxColumn, sizeof(auxColumn));
       numAuxiliaryColumns++;
+      pNew->numAuxiliaryColumns = numAuxiliaryColumns;
       user_column_idx++;
       continue;
     }
@@ -4842,6 +4860,7 @@ static int vec0_init(sqlite3 *db, void *pAux, int argc, const char *const *argv,
       pNew->user_column_idxs[user_column_idx] = numMetadataColumns;
       memcpy(&pNew->metadata_columns[numMetadataColumns], &metadataColumn, sizeof(metadataColumn));
       numMetadataColumns++;
+      pNew->numMetadataColumns = numMetadataColumns;
       user_column_idx++;
       continue;
     }