feat(mcp+lifecycle): MCP degraded-startup reporting, lane event schema, lane completion hardening

Add MCP structured degraded-startup classification (P2.10):
- classify MCP failures as startup/handshake/config/partial
- expose failed_servers + recovery_recommendations in tool output
- add mcp_degraded output field with server_name, failure_mode, recoverable

Canonical lane event schema (P2.7):
- add LaneEventName variants for all lifecycle states
- wire LaneEvent::new with full 3-arg signature (event, status, emitted_at)
- emit typed events for Started, Blocked, Failed, Finished

Fix let mut executor for search test binary
Fix lane_completion unused import warnings

Note: mcp_stdio::manager_discovery_report test has pre-existing failure on clean main, unrelated to this commit.

rust/crates/tools/src/lane_completion.rs

@@ -30,7 +30,9 @@ pub(crate) fn detect_lane_completion(
     }
     
     // Must have finished status
-    if output.status != "Finished" {
+    if !output.status.eq_ignore_ascii_case("completed")
+        && !output.status.eq_ignore_ascii_case("finished")
+    {
         return None;
     }
     
@@ -91,8 +93,7 @@ pub(crate) fn evaluate_completed_lane(
 mod tests {
     use super::*;
     use runtime::{DiffScope, LaneBlocker};
-    use crate::LaneEvent;
-    
+
     fn test_output() -> AgentOutput {
         AgentOutput {
             agent_id: "test-lane-1".to_string(),
@@ -176,4 +177,4 @@ mod tests {
         assert!(actions.contains(&PolicyAction::CloseoutLane));
         assert!(actions.contains(&PolicyAction::CleanupSession));
     }
-}
+}