feat: add verbose logging and complete observability (#251)

src/observability/verbose.rs

@@ -0,0 +1,96 @@
+use super::traits::{Observer, ObserverEvent, ObserverMetric};
+
+/// Human-readable progress observer for interactive CLI sessions.
+///
+/// This observer prints compact `>` / `<` progress lines without exposing
+/// prompt contents. It is intended to be opt-in (e.g. `--verbose`).
+pub struct VerboseObserver;
+
+impl VerboseObserver {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl Observer for VerboseObserver {
+    fn record_event(&self, event: &ObserverEvent) {
+        match event {
+            ObserverEvent::LlmRequest {
+                provider,
+                model,
+                messages_count,
+            } => {
+                eprintln!("> Thinking");
+                eprintln!(
+                    "> Send (provider={}, model={}, messages={})",
+                    provider, model, messages_count
+                );
+            }
+            ObserverEvent::LlmResponse {
+                duration, success, ..
+            } => {
+                let ms = u64::try_from(duration.as_millis()).unwrap_or(u64::MAX);
+                eprintln!("< Receive (success={success}, duration_ms={ms})");
+            }
+            ObserverEvent::ToolCallStart { tool } => {
+                eprintln!("> Tool {tool}");
+            }
+            ObserverEvent::ToolCall {
+                tool,
+                duration,
+                success,
+            } => {
+                let ms = u64::try_from(duration.as_millis()).unwrap_or(u64::MAX);
+                eprintln!("< Tool {tool} (success={success}, duration_ms={ms})");
+            }
+            ObserverEvent::TurnComplete => {
+                eprintln!("< Complete");
+            }
+            _ => {}
+        }
+    }
+
+    #[inline(always)]
+    fn record_metric(&self, _metric: &ObserverMetric) {}
+
+    fn name(&self) -> &str {
+        "verbose"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    #[test]
+    fn verbose_name() {
+        assert_eq!(VerboseObserver::new().name(), "verbose");
+    }
+
+    #[test]
+    fn verbose_events_do_not_panic() {
+        let obs = VerboseObserver::new();
+        obs.record_event(&ObserverEvent::LlmRequest {
+            provider: "openrouter".into(),
+            model: "claude".into(),
+            messages_count: 3,
+        });
+        obs.record_event(&ObserverEvent::LlmResponse {
+            provider: "openrouter".into(),
+            model: "claude".into(),
+            duration: Duration::from_millis(12),
+            success: true,
+            error_message: None,
+        });
+        obs.record_event(&ObserverEvent::ToolCallStart {
+            tool: "shell".into(),
+        });
+        obs.record_event(&ObserverEvent::ToolCall {
+            tool: "shell".into(),
+            duration: Duration::from_millis(2),
+            success: true,
+        });
+        obs.record_event(&ObserverEvent::TurnComplete);
+    }
+}