Mark the init functions' pApi unused under SQLITE_CORE

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Compiling `sqlite-vec.c` into SQLite or an application (`-DSQLITE_CORE`) with `-Wall -Wextra` builds without warnings; `sqlite3_vec_init()`, `sqlite3_vec_numpy_init()`, and `sqlite3_vec_static_blobs_init()` each warned that their `pApi` parameter was unused.
 - A KNN query that takes its query vector, `k`, or `mmr_lambda` from another table of a join now uses it. `select v.rowid from p join v on v.embedding match ? and v.k = p.k` failed with `A LIMIT or 'k = ?' constraint is required`; the same join with `v.k = 3 and v.mmr_lambda = p.lambda` returned no rows; and `select v.rowid from v join p on p.id = v.tag where v.embedding match p.vector and v.k = 2`, with `p.id` an integer primary key, could return no rows. These joins now run one KNN per row of the other table, so a filter on the `vec0` table whose value comes from that table applies before the k nearest rows are chosen. Ported in part from the unmerged [vlasky#14](https://github.com/vlasky/sqlite-vec/pull/14) ([asg017#331](https://github.com/asg017/sqlite-vec/pull/331)), which also applies filters whose value comes from a joined table before the k nearest rows are chosen; that part is not ported, and ARCHITECTURE.md's idxStr section says why.
 
 ## [2.1.1] - 2026-10-09

sqlite-vec.c

@@ -12525,6 +12525,8 @@ SQLITE_VEC_API int sqlite3_vec_init(sqlite3 *db, char **pzErrMsg,
                                     const sqlite3_api_routines *pApi) {
 #ifndef SQLITE_CORE
   SQLITE_EXTENSION_INIT2(pApi);
+#else
+  UNUSED_PARAMETER(pApi);
 #endif
   int rc = SQLITE_OK;
 
@@ -12611,6 +12613,8 @@ SQLITE_VEC_API int sqlite3_vec_numpy_init(sqlite3 *db, char **pzErrMsg,
   UNUSED_PARAMETER(pzErrMsg);
 #ifndef SQLITE_CORE
   SQLITE_EXTENSION_INIT2(pApi);
+#else
+  UNUSED_PARAMETER(pApi);
 #endif
   int rc = SQLITE_OK;
   rc = sqlite3_create_function_v2(db, "vec_npy_file", 1, SQLITE_RESULT_SUBTYPE,
@@ -12630,6 +12634,8 @@ sqlite3_vec_static_blobs_init(sqlite3 *db, char **pzErrMsg,
   UNUSED_PARAMETER(pzErrMsg);
 #ifndef SQLITE_CORE
   SQLITE_EXTENSION_INIT2(pApi);
+#else
+  UNUSED_PARAMETER(pApi);
 #endif
 
   int rc = SQLITE_OK;