feat: add FreeRTOS message bus (inbound + outbound queues)

mimi_msg_t carries channel/chat_id/content between tasks.
Decouples input channels from agent loop and output dispatch.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

main/bus/message_bus.c

@@ -0,0 +1,59 @@
+#include "message_bus.h"
+#include "mimi_config.h"
+#include "esp_log.h"
+#include <string.h>
+
+static const char *TAG = "bus";
+
+static QueueHandle_t s_inbound_queue;
+static QueueHandle_t s_outbound_queue;
+
+esp_err_t message_bus_init(void)
+{
+    s_inbound_queue = xQueueCreate(MIMI_BUS_QUEUE_LEN, sizeof(mimi_msg_t));
+    s_outbound_queue = xQueueCreate(MIMI_BUS_QUEUE_LEN, sizeof(mimi_msg_t));
+
+    if (!s_inbound_queue || !s_outbound_queue) {
+        ESP_LOGE(TAG, "Failed to create message queues");
+        return ESP_ERR_NO_MEM;
+    }
+
+    ESP_LOGI(TAG, "Message bus initialized (queue depth %d)", MIMI_BUS_QUEUE_LEN);
+    return ESP_OK;
+}
+
+esp_err_t message_bus_push_inbound(const mimi_msg_t *msg)
+{
+    if (xQueueSend(s_inbound_queue, msg, pdMS_TO_TICKS(1000)) != pdTRUE) {
+        ESP_LOGW(TAG, "Inbound queue full, dropping message");
+        return ESP_ERR_NO_MEM;
+    }
+    return ESP_OK;
+}
+
+esp_err_t message_bus_pop_inbound(mimi_msg_t *msg, uint32_t timeout_ms)
+{
+    TickType_t ticks = (timeout_ms == UINT32_MAX) ? portMAX_DELAY : pdMS_TO_TICKS(timeout_ms);
+    if (xQueueReceive(s_inbound_queue, msg, ticks) != pdTRUE) {
+        return ESP_ERR_TIMEOUT;
+    }
+    return ESP_OK;
+}
+
+esp_err_t message_bus_push_outbound(const mimi_msg_t *msg)
+{
+    if (xQueueSend(s_outbound_queue, msg, pdMS_TO_TICKS(1000)) != pdTRUE) {
+        ESP_LOGW(TAG, "Outbound queue full, dropping message");
+        return ESP_ERR_NO_MEM;
+    }
+    return ESP_OK;
+}
+
+esp_err_t message_bus_pop_outbound(mimi_msg_t *msg, uint32_t timeout_ms)
+{
+    TickType_t ticks = (timeout_ms == UINT32_MAX) ? portMAX_DELAY : pdMS_TO_TICKS(timeout_ms);
+    if (xQueueReceive(s_outbound_queue, msg, ticks) != pdTRUE) {
+        return ESP_ERR_TIMEOUT;
+    }
+    return ESP_OK;
+}

main/bus/message_bus.h

@@ -0,0 +1,46 @@
+#pragma once
+
+#include "esp_err.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/queue.h"
+
+/* Channel identifiers */
+#define MIMI_CHAN_TELEGRAM   "telegram"
+#define MIMI_CHAN_WEBSOCKET  "websocket"
+#define MIMI_CHAN_CLI        "cli"
+
+/* Message types on the bus */
+typedef struct {
+    char channel[16];       /* "telegram", "websocket", "cli" */
+    char chat_id[32];       /* Telegram chat_id or WS client id */
+    char *content;          /* Heap-allocated message text (caller must free) */
+} mimi_msg_t;
+
+/**
+ * Initialize the message bus (inbound + outbound FreeRTOS queues).
+ */
+esp_err_t message_bus_init(void);
+
+/**
+ * Push a message to the inbound queue (towards Agent Loop).
+ * The bus takes ownership of msg->content.
+ */
+esp_err_t message_bus_push_inbound(const mimi_msg_t *msg);
+
+/**
+ * Pop a message from the inbound queue (blocking).
+ * Caller must free msg->content when done.
+ */
+esp_err_t message_bus_pop_inbound(mimi_msg_t *msg, uint32_t timeout_ms);
+
+/**
+ * Push a message to the outbound queue (towards channels).
+ * The bus takes ownership of msg->content.
+ */
+esp_err_t message_bus_push_outbound(const mimi_msg_t *msg);
+
+/**
+ * Pop a message from the outbound queue (blocking).
+ * Caller must free msg->content when done.
+ */
+esp_err_t message_bus_pop_outbound(mimi_msg_t *msg, uint32_t timeout_ms);