joystick UI: drop dead members + refresh stale doc comments

JoystickUITask had two write-only fields after the recent refactors:
_msgcount (only reader getMsgCount() had no callers anywhere) and
_started_at (initialized, written in begin(), never read). Remove
both fields, their writes, and getMsgCount().

msgRead()'s auto-leave-Unread side-effect is preserved — it uses the
function parameter directly, not the field.

Also: update the loop() doc to drop the "calls poll()" reference and
the battery-cache comment to drop the "from housekeeping" wording —
both concepts gone since Phase C.

zephcore/helpers/ui-joystick/joystick_ui_task.cpp

@@ -199,12 +199,12 @@ JoystickUITask::JoystickUITask()
 	  _next_refresh(0), _screen_off_ms(AUTO_OFF_MILLIS), _was_display_on(false),
 	  _cached_batt_mv(0), _battery_display_mode(0),
 	  _brightness(100), _wake_on_msg(true), _ble_connected(false),
-	  _ble_enabled(true), _msgcount(0), _noise_floor(-120),
+	  _ble_enabled(true), _noise_floor(-120),
 	  _pkt_recv(0), _pkt_sent(0), _pkt_errors(0), _alert_expiry(0),
 	  _locked(false), _lock_step(0),
 	  _compose_is_contact(false), _compose_channel_idx(-1),
 	  _ch_preview_count(0), _ch_preview_head(JOYSTICK_OFFLINE_QUEUE_SIZE - 1),
-	  _started_at(0), _initialized(false)
+	  _initialized(false)
 {
 	memset(_alert, 0, sizeof(_alert));
 	memset(_compose_channel_name, 0, sizeof(_compose_channel_name));
@@ -222,7 +222,6 @@ void JoystickUITask::begin(BaseChatMesh *mesh, mesh::ZephyrRTCClock *rtc, NodePr
 	_mesh = mesh;
 	_rtc = rtc;
 	_prefs = prefs;
-	_started_at = k_uptime_get_32();
 
 	if (prefs && prefs->display_brightness >= 10) {
 		_brightness = prefs->display_brightness;
@@ -671,7 +670,7 @@ void JoystickUITask::toggleWakeOnMsg()
 /* ===== Notifications from mesh ===== */
 void JoystickUITask::newMsg(uint8_t path_len, const char *from_name, const char *text, int msgcount)
 {
-	_msgcount = msgcount;
+	(void)msgcount;  /* tracked by CompanionMesh; we mirror via msgRead() side-effect only */
 	if (_unread) {
 		/* When BLE phone is connected it pulls offline queue and marks read;
 		 * keep the message in our local history but don't count as unread. */
@@ -726,7 +725,9 @@ void JoystickUITask::newChannelMsg(const char *channel_name, const char *text,
 
 void JoystickUITask::msgRead(int msgcount)
 {
-	_msgcount = msgcount;
+	/* Called from CompanionMesh when the BLE-offline-queue drains to 0
+	 * (phone synced); auto-navigate home if the user is sitting on the
+	 * Unread list looking at what just got cleared. */
 	if (msgcount == 0 && _curr == _unread) {
 		gotoHomeScreen();
 	}

zephcore/helpers/ui-joystick/joystick_ui_task.h

@@ -44,7 +44,8 @@ public:
 	/* Call once after mesh/prefs are loaded */
 	void begin(BaseChatMesh *mesh, mesh::ZephyrRTCClock *rtc, NodePrefs *prefs);
 
-	/* Call from mesh event loop: processes input, renders, calls poll() */
+	/* Call from mesh event loop: drains the key queue, dispatches lifecycle
+	 * events on display-state transitions, and renders when due. */
 	void loop();
 
 	/* Called from CompanionMesh callbacks (mesh thread context) */
@@ -113,7 +114,6 @@ public:
 	/* Message / compose accessors */
 	int getUnreadCount();
 	int getStoredMsgCount() const;
-	int getMsgCount() const { return _msgcount; }
 	int getContactMsgCount(const char *contact_name) const;
 	bool getContactMsgAt(const char *contact_name, int idx, const char *&out_msg,
 		uint32_t &out_ts, uint8_t *out_path = nullptr) const;
@@ -145,7 +145,7 @@ public:
 	NodePrefs *getPrefs() const { return _prefs; }
 	JoystickDisplay &getDisplay() { return _display; }
 
-	/* Battery (updated via ui_set_battery from housekeeping) */
+	/* Battery cache (updated via ui_set_battery from ui_refresh_battery's render-path call) */
 	void setCachedBattMilliVolts(uint16_t mv) { _cached_batt_mv = mv; }
 
 	/* Radio stats (fed from main companion loop) */
@@ -239,7 +239,6 @@ private:
 	bool _wake_on_msg;
 	bool _ble_connected;
 	bool _ble_enabled;
-	int _msgcount;
 	int16_t _noise_floor;
 	uint32_t _pkt_recv, _pkt_sent, _pkt_errors;
 
@@ -293,6 +292,5 @@ private:
 	static struct k_msgq _key_queue;
 
 	/* Startup */
-	uint32_t _started_at;
 	bool _initialized;
 };