rag_ingest: Rewrite to use MySQL protocol (Sqlite_Server) instead of SQLite3 API

Convert rag_ingest from direct SQLite database access to MySQL protocol communication with SQLite Server.

Major changes:
- Replace SQLite3 direct API with MySQL/mariadb client library
- Update connection flow: rag_ingest -> MySQL protocol -> SQLite Server -> RAG DB
- Remove sqlite3 amalgamation dependency from rag_ingest target
- Keep all ingestion functionality intact (chunking, FTS5, vec0 embeddings)

Schema initialization:
- Add init command to create RAG schema via MySQL protocol
- Add ingest command to run data ingestion pipeline
- Add query command for vector similarity search with embeddings

RAG_POC/Makefile

@@ -6,14 +6,11 @@ ROOT_DIR := ..
 INCLUDES := \
 	-I$(ROOT_DIR)/deps/json \
 	-I$(ROOT_DIR)/deps/mariadb-client-library/mariadb_client/include \
-	-I$(ROOT_DIR)/deps/sqlite3/sqlite-amalgamation-3500400 \
 	-I$(ROOT_DIR)/deps/curl/curl/include
 
 LIBDIRS := \
 	-L$(ROOT_DIR)/deps/mariadb-client-library/mariadb_client/libmariadb
 
-SQLITE3_OBJ := $(ROOT_DIR)/deps/sqlite3/sqlite-amalgamation-3500400/sqlite3.o
-
 # Use static libcurl
 CURL_STATIC_LIB := $(ROOT_DIR)/deps/curl/curl/lib/.libs/libcurl.a
 
@@ -27,7 +24,7 @@ SOURCES := rag_ingest.cpp
 all: $(TARGET)
 
 $(TARGET): $(SOURCES)
-	$(CXX) $(CXXFLAGS) $(INCLUDES) $(LIBDIRS) $(SQLITE3_OBJ) $^ -o $@ $(LIBS)
+	$(CXX) $(CXXFLAGS) $(INCLUDES) $(LIBDIRS) $^ -o $@ $(LIBS)
 
 clean:
 	rm -f $(TARGET)

lib/proxy_sqlite3_symbols.cpp

@@ -50,9 +50,17 @@ int (*proxy_sqlite3_prepare_v2)(sqlite3*, const char*, int, sqlite3_stmt**, cons
 int (*proxy_sqlite3_open_v2)(const char*, sqlite3**, int, const char*) = sqlite3_open_v2;
 int (*proxy_sqlite3_exec)(sqlite3*, const char*, int (*)(void*,int,char**,char**), void*, char**) = sqlite3_exec;
 
-// Optional hooks used by sqlite-vec (function pointers will be set by LoadPlugin or remain NULL)
-void (*proxy_sqlite3_vec_init)(sqlite3*, char**, const sqlite3_api_routines*) = NULL;
-void (*proxy_sqlite3_rembed_init)(sqlite3*, char**, const sqlite3_api_routines*) = NULL;
+// Optional hooks used by sqlite-vec and sqlite-rembed
+// These are statically linked extensions that need to be initialized
+
+// Forward declarations for the extension init functions
+extern "C" int sqlite3_vec_init(sqlite3 *db, char **pzErrMsg, const sqlite3_api_routines *pApi);
+extern "C" int sqlite3_rembed_init(sqlite3 *db, char **pzErrMsg, const sqlite3_api_routines *pApi);
+
+// Initialize the extension pointers to the statically linked functions
+// These allow Admin_Bootstrap.cpp to register them as auto-extensions
+int (*proxy_sqlite3_vec_init)(sqlite3 *db, char **pzErrMsg, const sqlite3_api_routines *pApi) = sqlite3_vec_init;
+int (*proxy_sqlite3_rembed_init)(sqlite3 *db, char **pzErrMsg, const sqlite3_api_routines *pApi) = sqlite3_rembed_init;
 
 // Internal helpers used by admin stats batching; keep defaults as NULL