build(deps): always build sqlite-vec, not gated on PROXYSQLGENAI

Step 7 of the GenAI plugin carve-out made the sqlite-vec call site
in core unconditional (lib/proxy_sqlite3_symbols.cpp:58 includes
"sqlite-vec.h"; src/Makefile linkages $(SQLITE_VEC_OBJ) into
libproxysql.a unconditionally).  But deps/Makefile still gated the
ACTUAL build of vec.o + sqlite-vec.h on PROXYSQLGENAI=1, so
non-genai builds (debian12-dbg, ubuntu22-tap on the CI matrix)
failed at the lib step:

    proxy_sqlite3_symbols.cpp:58:10: fatal error: sqlite-vec.h:
        No such file or directory

Always pull sqlite-vec into the deps build (the existing
`sqlite-vec: sqlite3/sqlite3/vec.o` target stays for callers that
explicitly request it).  Per the design intent documented next to
$(SQLITE_VEC_OBJ) in src/Makefile: vec.o is always linked into
proxysql so the genai plugin (when dlopen'd) can call
sqlite3_vec_init on the same SQLite that core links against;
without the plugin loaded, the extension is dead code that doesn't
hurt non-genai installs.

deps/Makefile

@@ -49,9 +49,15 @@ ifeq ($(PROXYSQLCLICKHOUSE),1)
 	targets += clickhouse-cpp
 endif
 
-ifeq ($(PROXYSQLGENAI),1)
-	targets += sqlite-vec
-endif
+# sqlite-vec: vector similarity search extension.  Originally gated
+# behind PROXYSQLGENAI; Step 7 of the carve-out made the call site in
+# core (lib/proxy_sqlite3_symbols.cpp + lib/Admin_Bootstrap.cpp)
+# unconditional so the genai plugin (when dlopen'd) can call
+# sqlite3_vec_init on the same SQLite that proxysql linked against.
+# That requires vec.o + sqlite-vec.h to exist regardless of
+# PROXYSQLGENAI; otherwise non-genai dbg/release builds fail at
+# `#include "sqlite-vec.h"`.  Always build it.
+targets += sqlite-vec
 
 default: $(targets)
 .PHONY: default
@@ -281,13 +287,16 @@ sqlite3/sqlite3/vec.o: sqlite3/sqlite3/sqlite3.o
 	cd sqlite3/sqlite3 && cp ../sqlite-vec-source/sqlite-vec.c . && cp ../sqlite-vec-source/sqlite-vec.h .
 	cd sqlite3/sqlite3 && ${CC} ${MYCFLAGS} -fPIC -c -o vec.o sqlite-vec.c -DSQLITE_CORE -DSQLITE_VEC_STATIC -DSQLITE_ENABLE_MEMORY_MANAGEMENT -DSQLITE_ENABLE_JSON1 -DSQLITE_ENABLE_FTS5 -DSQLITE_DLL=1
 
-ifeq ($(PROXYSQLGENAI),1)
+# Step 7: vec.o is unconditionally linked into proxysql (see
+# src/Makefile $(SQLITE_VEC_OBJ)), so we always build it as part of
+# the sqlite3 target — no longer gated on PROXYSQLGENAI.  Without
+# this, non-genai dbg builds find sqlite-vec.h missing when
+# lib/proxy_sqlite3_symbols.cpp tries to `#include "sqlite-vec.h"`.
 sqlite3: sqlite3/sqlite3/sqlite3.o sqlite3/sqlite3/vec.o
-else
-sqlite3: sqlite3/sqlite3/sqlite3.o
-endif
 
-# sqlite-vec: Vector similarity search extension (for GenAI)
+# sqlite-vec: Vector similarity search extension.  Kept as a separate
+# target name so existing callers (top-level Makefile, packaging
+# entrypoints) keep working; sqlite3 above already pulls in vec.o.
 sqlite-vec: sqlite3/sqlite3/vec.o