Kernel improvements (#485)

* **New Features**
  * Added public accessors for querying module/device start and ready state.

* **Refactor**
  * Internal state moved to opaque internal objects; module/device/driver initializers now explicitly initialize internal pointers.
  * Lifecycle handling updated to construct/destruct internal state and use accessors.

* **Tests**
  * Tests updated to use public accessors and explicit construct/destruct lifecycle calls.

* **Chores**
  * Test build/include paths and small metadata updated.

TactilityKernel/Include/tactility/concurrent/mutex.h

@@ -18,12 +18,10 @@ struct Mutex {
 };
 
 inline static void mutex_construct(struct Mutex* mutex) {
-    assert(mutex->handle == NULL);
     mutex->handle = xSemaphoreCreateMutex();
 }
 
 inline static void mutex_destruct(struct Mutex* mutex) {
-    assert(mutex->handle != NULL);
     vPortAssertIfInISR();
     vSemaphoreDelete(mutex->handle);
     mutex->handle = NULL;

TactilityKernel/Include/tactility/device.h

@@ -16,39 +16,30 @@ extern "C" {
 #endif
 
 struct Driver;
-struct DevicePrivate;
+struct DeviceInternal;
 
 /** Enables discovering devices of the same type */
 struct DeviceType {
-    /* Placeholder because empty structs have a different size with C vs C++ compilers */
-    uint8_t _;
+    const char* name;
 };
 
 /** Represents a piece of hardware */
 struct Device {
     /** The name of the device. Valid characters: a-z a-Z 0-9 - _ . */
     const char* name;
+
     /** The configuration data for the device's driver */
     const void* config;
+
     /** The parent device that this device belongs to. Can be NULL, but only the root device should have a NULL parent. */
     struct Device* parent;
-    /** Internal data */
-    struct {
-        /** Address of the API exposed by the device instance. */
-        struct Driver* driver;
-        /** The driver data for this device (e.g. a mutex) */
-        void* driver_data;
-        /** The mutex for device operations */
-        struct Mutex mutex;
-        /** The device state */
-        struct {
-            int start_result;
-            bool started : 1;
-            bool added : 1;
-        } state;
-        /** Private data */
-        struct DevicePrivate* device_private;
-    } internal;
+
+    /**
+     * Internal state managed by the kernel.
+     * Device implementers should initialize this to NULL.
+     * Do not access or modify directly; use device_* functions.
+     */
+    struct DeviceInternal* internal;
 };
 
 /**

TactilityKernel/Include/tactility/driver.h

@@ -12,7 +12,7 @@ extern "C" {
 struct Device;
 struct DeviceType;
 struct Module;
-struct DriverPrivate;
+struct DriverInternal;
 
 struct Driver {
     /** The driver name */
@@ -29,8 +29,12 @@ struct Driver {
     const struct DeviceType* device_type;
     /** The module that owns this driver. When it is NULL, the system owns the driver and it cannot be removed from registration. */
     const struct Module* owner;
-    /** Internal data */
-    struct DriverPrivate* driver_private;
+    /**
+     * Internal state managed by the kernel.
+     * Driver implementers should initialize this to NULL.
+     * Do not access or modify directly; use driver_* functions.
+     */
+    struct DriverInternal* internal;
 };
 
 /**

TactilityKernel/Include/tactility/module.h

@@ -25,6 +25,8 @@ struct ModuleSymbol {
     const void* symbol;
 };
 
+struct ModuleInternal;
+
 /**
  * A module is a collection of drivers or other functionality that can be loaded and unloaded at runtime.
  */
@@ -36,7 +38,6 @@ struct Module {
      * Desirable format "platform-esp32", "lilygo-tdeck", etc.
      */
     const char* name;
-
     /**
      * A function to initialize the module.
      * Should never be NULL.
@@ -44,24 +45,24 @@ struct Module {
      * @return ERROR_NONE if successful
      */
     error_t (*start)(void);
-
     /**
      * Deinitializes the module.
      * Should never be NULL.
      * @return ERROR_NONE if successful
      */
     error_t (*stop)(void);
-
     /**
      * A list of symbols exported by the module.
      * Should be terminated by MODULE_SYMBOL_TERMINATOR.
      * Can be a NULL value.
      */
     const struct ModuleSymbol* symbols;
-
-    struct {
-        bool started;
-    } internal;
+    /**
+     * Internal state managed by the kernel.
+     * Module implementers should initialize this to NULL.
+     * Do not access or modify directly; use module_* functions.
+     */
+    struct ModuleInternal* internal;
 };
 
 /**