feat(ui): add EventLine struct and UiEvent::Event variant

Add the EventLine data type for the upcoming Events panel with category,
message, timestamp, and is_error fields. Add the Event(EventLine) variant
to UiEvent and a pub re-export from ui::mod. Include a no-op match arm
in state::apply() to maintain exhaustive matching, and a basic PartialEq
test for EventLine.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: d4ncer

src/ui/event.rs

@@ -9,6 +9,20 @@ pub struct ToolLine {
     pub summary: String,
 }
 
+/// A structured event entry for the Events panel.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct EventLine {
+    /// Category label: "task", "iter", "feature", "verify", "review",
+    /// "journal", "knowledge", "interrupt", "dag", "config".
+    pub category: String,
+    /// Pre-formatted message with template variables already substituted.
+    pub message: String,
+    /// Local timestamp formatted as "HH:MM:SS".
+    pub timestamp: String,
+    /// If true, render message in error style (red) instead of info style.
+    pub is_error: bool,
+}
+
 /// Event payload rendered by the TUI.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum UiEvent {
@@ -25,4 +39,31 @@ pub enum UiEvent {
     IterationDivider {
         iteration: u32,
     },
+    /// Structured orchestration event for the Events panel.
+    Event(EventLine),
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn event_line_partial_eq() {
+        let a = EventLine {
+            category: "task".to_string(),
+            message: "t-abcd1234 claimed".to_string(),
+            timestamp: "14:32:05".to_string(),
+            is_error: false,
+        };
+        let b = a.clone();
+        assert_eq!(a, b);
+
+        let c = EventLine {
+            category: "task".to_string(),
+            message: "t-abcd1234 claimed".to_string(),
+            timestamp: "14:32:05".to_string(),
+            is_error: true,
+        };
+        assert_ne!(a, c);
+    }
 }

src/ui/mod.rs

@@ -12,6 +12,7 @@ use std::sync::mpsc::{self, Sender};
 use std::sync::{Mutex, OnceLock};
 use std::thread::JoinHandle;
 
+pub use event::EventLine;
 pub use event::UiEvent;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]

src/ui/state.rs

@@ -167,6 +167,9 @@ impl AppState {
                     self.tools.pop_front();
                 }
             }
+            UiEvent::Event(_) => {
+                // TODO: Events panel state management (Phase 1 state task)
+            }
         }
     }