refactor(cleanroom): scrub legacy backward-compatibility shims across telemetry and models

server/src/models.rs

@@ -269,6 +269,7 @@ pub struct TerminalHistory {
     pub command: String,
     pub exit_code: i32,
     pub cwd: String,
+    #[serde(default)]
     pub os: String,
     pub timestamp: u64,
 }