fix: add 100ms delay after ALSA Direct PCM release before CPAL fallback

When ALSA Direct opens a PCM device and fails to configure the rate,
the PCM handle is dropped but the kernel may not release the device
instantly. CPAL then fails with "Device busy" when trying to open it.

Add 100ms sleep after InvalidParams to let the kernel fully release
the device before CPAL attempts to open it. Also fix error messages
to show the effective (fallback) rate instead of the original rate.

crates/qbz-audio/src/alsa_backend.rs

@@ -530,10 +530,13 @@ impl AlsaBackend {
                         // Hardware doesn't support this rate/format natively.
                         // Return None to let the player fall back to CPAL/rodio
                         // which can resample (e.g. 176.4kHz → 88.2kHz).
+                        // Brief delay: ALSA Direct opened the PCM (then failed to configure it).
+                        // The kernel needs a moment to fully release the device before CPAL can open it.
                         log::info!(
-                            "[ALSA Backend] Hardware doesn't support {}Hz natively, falling back to CPAL (will resample)",
+                            "[ALSA Backend] Hardware doesn't support {}Hz natively, releasing device for CPAL fallback",
                             config.sample_rate
                         );
+                        std::thread::sleep(std::time::Duration::from_millis(100));
                         return None;
                     }
 
@@ -595,9 +598,10 @@ impl AlsaBackend {
                     // Return None to let the player fall back to CPAL/rodio
                     // which can resample (e.g. 176.4kHz → 88.2kHz).
                     log::info!(
-                        "[ALSA Backend] Hardware doesn't support {}Hz even via plughw, falling back to CPAL (will resample)",
+                        "[ALSA Backend] Hardware doesn't support {}Hz even via plughw, releasing device for CPAL fallback",
                         config.sample_rate
                     );
+                    std::thread::sleep(std::time::Duration::from_millis(100));
                     return None;
                 }
 
@@ -798,10 +802,10 @@ impl AudioBackend for AlsaBackend {
                 if config.exclusive_mode {
                     format!(
                         "Failed to create exclusive ALSA stream at {}Hz: {}. Device may be in use by another application.",
-                        config.sample_rate, e
+                        effective_rate, e
                     )
                 } else {
-                    format!("Failed to create ALSA device sink builder at {}Hz: {}", config.sample_rate, e)
+                    format!("Failed to create ALSA device sink builder at {}Hz: {}", effective_rate, e)
                 }
             })?
             .with_supported_config(&supported_config)
@@ -810,10 +814,10 @@ impl AudioBackend for AlsaBackend {
                 if config.exclusive_mode {
                     format!(
                         "Failed to create exclusive ALSA stream at {}Hz: {}. Device may be in use by another application.",
-                        config.sample_rate, e
+                        effective_rate, e
                     )
                 } else {
-                    format!("Failed to create ALSA stream at {}Hz: {}", config.sample_rate, e)
+                    format!("Failed to create ALSA stream at {}Hz: {}", effective_rate, e)
                 }
             })?;