feat: enhance agent personality, tool guidance, and memory hygiene

- Expand communication style presets (professional, expressive, custom)
- Enrich SOUL.md with human-like tone and emoji-awareness guidance
- Add crash recovery and sub-task scoping guidance to AGENTS.md scaffold
- Add 'Use when / Don't use when' guidance to TOOLS.md and runtime prompts
- Implement memory hygiene system with configurable archiving and retention
- Add MemoryConfig options: hygiene_enabled, archive_after_days, purge_after_days, conversation_retention_days
- Archive old daily memory and session files to archive subdirectories
- Purge old archives and prune stale SQLite conversation rows
- Add comprehensive tests for new features

src/providers/reliable.rs

@@ -0,0 +1,229 @@
+use super::Provider;
+use async_trait::async_trait;
+use std::time::Duration;
+
+/// Provider wrapper with retry + fallback behavior.
+pub struct ReliableProvider {
+    providers: Vec<(String, Box<dyn Provider>)>,
+    max_retries: u32,
+    base_backoff_ms: u64,
+}
+
+impl ReliableProvider {
+    pub fn new(
+        providers: Vec<(String, Box<dyn Provider>)>,
+        max_retries: u32,
+        base_backoff_ms: u64,
+    ) -> Self {
+        Self {
+            providers,
+            max_retries,
+            base_backoff_ms: base_backoff_ms.max(50),
+        }
+    }
+}
+
+#[async_trait]
+impl Provider for ReliableProvider {
+    async fn chat_with_system(
+        &self,
+        system_prompt: Option<&str>,
+        message: &str,
+        model: &str,
+        temperature: f64,
+    ) -> anyhow::Result<String> {
+        let mut failures = Vec::new();
+
+        for (provider_name, provider) in &self.providers {
+            let mut backoff_ms = self.base_backoff_ms;
+
+            for attempt in 0..=self.max_retries {
+                match provider
+                    .chat_with_system(system_prompt, message, model, temperature)
+                    .await
+                {
+                    Ok(resp) => {
+                        if attempt > 0 {
+                            tracing::info!(
+                                provider = provider_name,
+                                attempt,
+                                "Provider recovered after retries"
+                            );
+                        }
+                        return Ok(resp);
+                    }
+                    Err(e) => {
+                        failures.push(format!(
+                            "{provider_name} attempt {}/{}: {e}",
+                            attempt + 1,
+                            self.max_retries + 1
+                        ));
+
+                        if attempt < self.max_retries {
+                            tracing::warn!(
+                                provider = provider_name,
+                                attempt = attempt + 1,
+                                max_retries = self.max_retries,
+                                "Provider call failed, retrying"
+                            );
+                            tokio::time::sleep(Duration::from_millis(backoff_ms)).await;
+                            backoff_ms = (backoff_ms.saturating_mul(2)).min(10_000);
+                        }
+                    }
+                }
+            }
+
+            tracing::warn!(provider = provider_name, "Switching to fallback provider");
+        }
+
+        anyhow::bail!("All providers failed. Attempts:\n{}", failures.join("\n"))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::sync::atomic::{AtomicUsize, Ordering};
+    use std::sync::Arc;
+
+    struct MockProvider {
+        calls: Arc<AtomicUsize>,
+        fail_until_attempt: usize,
+        response: &'static str,
+        error: &'static str,
+    }
+
+    #[async_trait]
+    impl Provider for MockProvider {
+        async fn chat_with_system(
+            &self,
+            _system_prompt: Option<&str>,
+            _message: &str,
+            _model: &str,
+            _temperature: f64,
+        ) -> anyhow::Result<String> {
+            let attempt = self.calls.fetch_add(1, Ordering::SeqCst) + 1;
+            if attempt <= self.fail_until_attempt {
+                anyhow::bail!(self.error);
+            }
+            Ok(self.response.to_string())
+        }
+    }
+
+    #[tokio::test]
+    async fn succeeds_without_retry() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let provider = ReliableProvider::new(
+            vec![(
+                "primary".into(),
+                Box::new(MockProvider {
+                    calls: Arc::clone(&calls),
+                    fail_until_attempt: 0,
+                    response: "ok",
+                    error: "boom",
+                }),
+            )],
+            2,
+            1,
+        );
+
+        let result = provider.chat("hello", "test", 0.0).await.unwrap();
+        assert_eq!(result, "ok");
+        assert_eq!(calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn retries_then_recovers() {
+        let calls = Arc::new(AtomicUsize::new(0));
+        let provider = ReliableProvider::new(
+            vec![(
+                "primary".into(),
+                Box::new(MockProvider {
+                    calls: Arc::clone(&calls),
+                    fail_until_attempt: 1,
+                    response: "recovered",
+                    error: "temporary",
+                }),
+            )],
+            2,
+            1,
+        );
+
+        let result = provider.chat("hello", "test", 0.0).await.unwrap();
+        assert_eq!(result, "recovered");
+        assert_eq!(calls.load(Ordering::SeqCst), 2);
+    }
+
+    #[tokio::test]
+    async fn falls_back_after_retries_exhausted() {
+        let primary_calls = Arc::new(AtomicUsize::new(0));
+        let fallback_calls = Arc::new(AtomicUsize::new(0));
+
+        let provider = ReliableProvider::new(
+            vec![
+                (
+                    "primary".into(),
+                    Box::new(MockProvider {
+                        calls: Arc::clone(&primary_calls),
+                        fail_until_attempt: usize::MAX,
+                        response: "never",
+                        error: "primary down",
+                    }),
+                ),
+                (
+                    "fallback".into(),
+                    Box::new(MockProvider {
+                        calls: Arc::clone(&fallback_calls),
+                        fail_until_attempt: 0,
+                        response: "from fallback",
+                        error: "fallback down",
+                    }),
+                ),
+            ],
+            1,
+            1,
+        );
+
+        let result = provider.chat("hello", "test", 0.0).await.unwrap();
+        assert_eq!(result, "from fallback");
+        assert_eq!(primary_calls.load(Ordering::SeqCst), 2);
+        assert_eq!(fallback_calls.load(Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn returns_aggregated_error_when_all_providers_fail() {
+        let provider = ReliableProvider::new(
+            vec![
+                (
+                    "p1".into(),
+                    Box::new(MockProvider {
+                        calls: Arc::new(AtomicUsize::new(0)),
+                        fail_until_attempt: usize::MAX,
+                        response: "never",
+                        error: "p1 error",
+                    }),
+                ),
+                (
+                    "p2".into(),
+                    Box::new(MockProvider {
+                        calls: Arc::new(AtomicUsize::new(0)),
+                        fail_until_attempt: usize::MAX,
+                        response: "never",
+                        error: "p2 error",
+                    }),
+                ),
+            ],
+            0,
+            1,
+        );
+
+        let err = provider
+            .chat("hello", "test", 0.0)
+            .await
+            .expect_err("all providers should fail");
+        let msg = err.to_string();
+        assert!(msg.contains("All providers failed"));
+        assert!(msg.contains("p1 attempt 1/1"));
+        assert!(msg.contains("p2 attempt 1/1"));
+    }
+}