feat: local TTS via piper subprocess with Google fallback

- New src/tts.rs: centralize TTS in synthesize(config, http_client, text)
  Piper subprocess primary, Google Translate fallback on error/missing
- TTS_MODEL_PATH/TTS_VOICE env config (defaults to pl_PL-bass-high)
- Fix Unknown interaction errors: spawn play_tts_in_channel in background
  so voice-state TTS no longer blocks the shard event loop (3s Discord limit)
- Best-effort confirmation replies in /tts to prevent error cascade
- Custom on_error handler: graceful interaction-expired error handling
- Comprehensive tracing logging (engine, model, duration, stderr)

1 files changed, 31 insertions, 7 deletions

diff --git a/src/main.rs b/src/main.rs
index d06176d..31c9e94 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,6 +15,7 @@ mod events;
 mod lang;
 mod openrouter;
 mod tasks;
+mod tts;
 mod voice;
 
 use database::DbPool;
@@ -26,9 +27,7 @@ const AC_SEARCH_CACHE_TTL: Duration = Duration::from_secs(10);
 type AcCache = tokio::sync::Mutex<HashMap<(serenity::UserId, String), copyparty::SearchHit>>;
 
 /// Shared autocomplete search cache: query → (hits, cached_at).
-type AcSearchCache = Arc<
-    tokio::sync::Mutex<HashMap<String, (Vec<copyparty::SearchHit>, Instant)>>,
->;
+type AcSearchCache = Arc<tokio::sync::Mutex<HashMap<String, (Vec<copyparty::SearchHit>, Instant)>>>;
 
 pub struct Data {
     pub db_pool: DbPool,
@@ -84,10 +83,7 @@ impl Data {
 
     /// Look up search cache for an autocomplete query. Returns `None` if
     /// uncached or stale.
-    pub async fn ac_search_cache_lookup(
-        &self,
-        query: &str,
-    ) -> Option<Vec<copyparty::SearchHit>> {
+    pub async fn ac_search_cache_lookup(&self, query: &str) -> Option<Vec<copyparty::SearchHit>> {
         let cache = self.ac_search_cache.lock().await;
         let (hits, cached_at) = cache.get(query)?;
         if cached_at.elapsed() > AC_SEARCH_CACHE_TTL {
@@ -150,6 +146,34 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                     Ok(())
                 })
             },
+            on_error: |error| {
+                Box::pin(async move {
+                    match error {
+                        poise::FrameworkError::Command { ctx, error, .. } => {
+                            tracing::error!(command = %ctx.command().name, "Command failed: {error}");
+                            if let Err(e) = ctx
+                                .send(
+                                    poise::CreateReply::default()
+                                        .content(format!("Błąd: {error}"))
+                                        .ephemeral(true),
+                                )
+                                .await
+                            {
+                                tracing::debug!(
+                                    "Could not send error reply (interaction likely expired): {e}"
+                                );
+                            }
+                        }
+                        other => {
+                            if let Err(e) = poise::builtins::on_error(other).await {
+                                tracing::warn!(
+                                    "Error while sending error message (interaction likely expired): {e}"
+                                );
+                            }
+                        }
+                    }
+                })
+            },
             ..Default::default()
         })
         .setup(move |ctx, _ready, framework| {