fix(424): add throttled field to all StoryAgent ctors and handle HardBlock in ws.rs

The initial commit added the `throttled` field to `StoryAgent` but missed
several construction sites in lifecycle.rs, test_helpers.rs, and scan.rs.
Also adds the `HardBlock` match arm in the WebSocket event conversion and
minor CSS/import ordering fixes.

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

server/src/agents/pool/test_helpers.rs

@@ -33,6 +33,7 @@ impl AgentPool {
                 project_root: None,
                 log_session_id: None,
                 merge_failure_reported: false,
+                throttled: false,
             },
         );
         tx
@@ -68,6 +69,7 @@ impl AgentPool {
                 project_root: None,
                 log_session_id: None,
                 merge_failure_reported: false,
+                throttled: false,
             },
         );
         tx
@@ -100,6 +102,7 @@ impl AgentPool {
                 project_root: Some(project_root),
                 log_session_id: None,
                 merge_failure_reported: false,
+                throttled: false,
             },
         );
         tx
@@ -131,6 +134,7 @@ impl AgentPool {
                 project_root: None,
                 log_session_id: None,
                 merge_failure_reported: false,
+                throttled: false,
             },
         );
         tx