chore: add comments for test model usage

Added comments clarifying the use of a lightweight model for testing in both the Makefile and unittest.c. Reordered and grouped related test variables in the Makefile for better readability.

Author: andinux

Makefile

@@ -29,12 +29,6 @@ SRC_DIR = src
 DIST_DIR = dist
 VPATH = $(SRC_DIR)
 BUILD_DIR = build
-CTEST_BIN = $(BUILD_DIR)/tests/sqlite_ai_tests
-GGUF_MODEL_DIR ?= tests/models/unsloth/gemma-3-270m-it-GGUF
-GGUF_MODEL_NAME ?= gemma-3-270m-it-UD-IQ2_M.gguf
-GGUF_MODEL_URL ?= https://huggingface.co/unsloth/gemma-3-270m-it-GGUF/resolve/main/gemma-3-270m-it-UD-IQ2_M.gguf
-GGUF_MODEL_PATH := $(GGUF_MODEL_DIR)/$(GGUF_MODEL_NAME)
-SKIP_UNITTEST ?= 0
 LLAMA_DIR = modules/llama.cpp
 WHISPER_DIR = modules/whisper.cpp
 MINIAUDIO_DIR = modules/miniaudio
@@ -43,6 +37,15 @@ BUILD_LLAMA = $(BUILD_DIR)/llama.cpp
 BUILD_WHISPER = $(BUILD_DIR)/whisper.cpp
 BUILD_MINIAUDIO = $(BUILD_DIR)/miniaudio
 
+# Test 
+# gemma-3-270m-it-UD-IQ2_M.gguf is just a lightweight model to use for testing
+CTEST_BIN = $(BUILD_DIR)/tests/sqlite_ai_tests
+GGUF_MODEL_DIR ?= tests/models/unsloth/gemma-3-270m-it-GGUF
+GGUF_MODEL_NAME ?= gemma-3-270m-it-UD-IQ2_M.gguf
+GGUF_MODEL_URL ?= https://huggingface.co/unsloth/gemma-3-270m-it-GGUF/resolve/main/gemma-3-270m-it-UD-IQ2_M.gguf
+GGUF_MODEL_PATH := $(GGUF_MODEL_DIR)/$(GGUF_MODEL_NAME)
+SKIP_UNITTEST ?= 0
+
 # Compiler and flags
 CC = gcc
 CXX = g++

tests/c/unittest.c

@@ -9,6 +9,7 @@
 #include "sqlite-ai.h"
 #endif
 
+// Just a lightweight model to use for testing
 #define DEFAULT_MODEL_PATH "tests/models/unsloth/gemma-3-270m-it-GGUF/gemma-3-270m-it-UD-IQ2_M.gguf"
 
 typedef struct {