Add Slice 4 tuner stack with AGENTS-compliant core types and HTTP API.

Introduces Si4684/ADAU1701 drivers, TunerService, FrequencyKHz,
SeekDirection, /api/tuner routes without file-scope globals, host tests,
and firmware blob tooling (binaries remain gitignored).

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/drivers/adau1701/CMakeLists.txt

@@ -1,6 +1,14 @@
+set(ADAU_FW_DIR "${CMAKE_CURRENT_LIST_DIR}/../../../Firmware/ADAU1701-Firmware")
+
 idf_component_register(
-    SRCS "src/component_stub.cpp"
-    INCLUDE_DIRS "include"
+    SRCS
+        "src/Adau1701Driver.cpp"
+        "src/SigmaStudioFW.c"
+        "src/adau1701_program.c"
+    INCLUDE_DIRS
+        "include"
+        "${ADAU_FW_DIR}"
+    REQUIRES driver esp_driver_gpio esp_driver_i2c
 )
 
 target_compile_features(${COMPONENT_LIB} PUBLIC cxx_std_23)