✨ feat(uart): add UART availability check, inter-step delays, and post-download Zynq status verification

- Add check_uart_available() to serial_monitor.py — detects port availability
- Add verify_zynq_status() to boot_verifier.py — lightweight post-download check
- Add uart_delay / inter_step_delay config fields (defaults: 3s / 2s)
- Step 1: Check UART availability, show non-blocking 'UART 不可用' notification
- Step 4: Add post-download Zynq status check (ping + serial) after TFTP
- _run_steps_worker: Add configurable inter-step delays between all steps
- Update step labels (4a→4b→4c→4d) for clarity

src/boot_verifier.py

@@ -124,6 +124,100 @@ def verify_boot(
     )
 
 
+def verify_zynq_status(
+    config: Config,
+    timeout: int | None = None,
+    max_retries: int = 3,
+    uart_available: bool = True,
+    callback: ProgressCallback = None,
+) -> BootVerificationResult:
+    """Quickly verify Zynq is responding after a download operation.
+
+    Performs a fast ping check and optionally a serial port read.
+    Unlike verify_boot, this is a lightweight check meant to confirm
+    the device is alive after flash/TFTP operations (before reboot).
+
+    Args:
+        config: Application configuration.
+        timeout: Seconds per ping attempt.
+        max_retries: Number of ping retry attempts.
+        uart_available: Whether UART serial port is available.
+        callback: Optional progress callback.
+
+    Returns:
+        BootVerificationResult (ip_reachable and serial_found reflect
+        the quick check results).
+    """
+    timeout = timeout or config.ping_timeout
+    ip = config.zynq_ip
+
+    if callback:
+        callback("start", f"Checking Zynq status on {ip}...")
+
+    # Check 1: Ping
+    ip_reachable = False
+    for attempt in range(1, max_retries + 1):
+        if callback:
+            callback("progress", f"Ping attempt {attempt}/{max_retries}...")
+        if ping_ip(ip, 1, timeout):
+            ip_reachable = True
+            if callback:
+                callback("complete", f"Device {ip} is reachable")
+            break
+        time.sleep(1)
+
+    # Check 2: Serial (only if UART is available)
+    serial_found = False
+    boot_info: dict = {}
+    if uart_available and config.serial_port:
+        ports = detect_serial_ports()
+        if ports:
+            for port_info in ports:
+                if port_info.device == config.serial_port:
+                    try:
+                        lines = read_serial_stream(
+                            config.serial_port,
+                            config.serial_baudrate,
+                            timeout=3,
+                        )
+                        parsed = parse_boot_output(lines)
+                        if parsed.ip_address or parsed.boot_message or parsed.version:
+                            serial_found = True
+                            boot_info = {
+                                "ip_address": parsed.ip_address,
+                                "version": parsed.version,
+                                "boot_message": parsed.boot_message,
+                                "raw_lines": lines[-20:],
+                            }
+                            if callback:
+                                callback("complete", "Boot messages detected on serial")
+                            break
+                    except Exception:
+                        pass  # Non-fatal; fall through
+
+    success = ip_reachable or serial_found
+    message_parts = []
+    if ip_reachable:
+        message_parts.append(f"IP {ip} reachable")
+    if serial_found:
+        message_parts.append("serial boot info found")
+    if not success:
+        message_parts.append("Zynq not responding")
+
+    message = "; ".join(message_parts) if message_parts else "Check inconclusive"
+
+    if callback:
+        callback("complete" if success else "error", message)
+
+    return BootVerificationResult(
+        success=success,
+        message=message,
+        ip_reachable=ip_reachable,
+        serial_found=serial_found,
+        boot_info=boot_info if boot_info else {},
+    )
+
+
 def wait_for_boot(
     config: Config,
     timeout: int | None = None,