Add BMA456 tap detection with ESP-NOW notify and host snapshot API.

Slaves forward configured tap kinds to the master; goTool exposes CLI, dashboard, REST, and WebSocket with separate notify vs receive and 2s display cache.

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

main/client_registry.h

@@ -30,6 +30,14 @@ typedef struct {
   uint32_t accel_updated_at;
   /** Host-enabled ESP-NOW accel stream to master. */
   bool accel_stream_enabled;
+  /** Host-enabled ESP-NOW tap notify flags. */
+  bool tap_notify_single;
+  bool tap_notify_double;
+  bool tap_notify_triple;
+  /** Latest tap from slave ESP-NOW (master only, short-lived cache). */
+  bool tap_valid;
+  uint32_t tap_kind;
+  uint32_t tap_updated_at;
   /** Latest LiPo ADC from slave ESP-NOW battery report (~30 s). */
   bool lipo1_valid;
   bool lipo2_valid;
@@ -39,6 +47,8 @@ typedef struct {
 } client_info_t;
 
 #define CLIENT_REGISTRY_DEFAULT_ACCEL_DEADZONE 100u
+/** Tap events older than this are discarded (matches accel stream interval). */
+#define CLIENT_REGISTRY_TAP_MAX_AGE_MS 16u
 
 void client_registry_init(void);
 
@@ -87,6 +97,31 @@ esp_err_t client_registry_set_accel_stream(uint32_t client_id, bool enabled);
 esp_err_t client_registry_get_accel_stream(uint32_t client_id, bool *enabled_out);
 size_t client_registry_set_accel_stream_all(bool enabled);
 
+esp_err_t client_registry_set_tap_notify(uint32_t client_id, bool single,
+                                         bool double_tap, bool triple);
+esp_err_t client_registry_get_tap_notify(uint32_t client_id, bool *single_out,
+                                         bool *double_tap_out,
+                                         bool *triple_out);
+size_t client_registry_set_tap_notify_all(bool single, bool double_tap,
+                                          bool triple);
+
+/** Store tap event from slave (matched by sender MAC). kind: 1=single, 2=double, 3=triple. */
+esp_err_t client_registry_update_tap(const uint8_t mac[CLIENT_MAC_LEN],
+                                     uint32_t slave_id, uint32_t kind);
+
+/** Drop cached tap if older than CLIENT_REGISTRY_TAP_MAX_AGE_MS. */
+void client_registry_expire_tap(client_info_t *info);
+
+/** Clear cached tap after UART snapshot or expiry. */
+void client_registry_clear_tap(client_info_t *info);
+
+/**
+ * If client has a fresh tap (age <= CLIENT_REGISTRY_TAP_MAX_AGE_MS), copy it out
+ * and clear the cache. Returns true when an event was returned.
+ */
+bool client_registry_take_tap(uint32_t client_id, uint32_t *kind_out,
+                              uint32_t *age_ms_out);
+
 /** Master local LiPo (client_id 0 in UART battery responses). */
 void client_registry_set_master_battery(const board_lipo_reading_t *reading);
 bool client_registry_get_master_battery(board_lipo_reading_t *reading_out,