ci: address Copilot review suggestions on instructions file

- Add missing tracing macro variants (warn!, error!) and unqualified
  forms (info!, debug!, warn!, error! via use tracing::{...})
- Fix error handling section: separate silently-swallowed errors
  (.ok(), let _ = result) from panicking operations (.unwrap()/.expect())

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

Author: litianningdatadog

.github/copilot-instructions.md

@@ -3,7 +3,9 @@
 ## Security — PII and Secrets
 
 Flag any logging statements (`log::info!`, `log::debug!`, `log::warn!`, `log::error!`,
-`tracing::info!`, `tracing::debug!`) that may log:
+`tracing::info!`, `tracing::debug!`, `tracing::warn!`, `tracing::error!`, or unqualified
+`info!`, `debug!`, `warn!`, `error!` macros (e.g., via `use tracing::{info, debug, warn, error}`))
+that may log:
 - HTTP request/response headers (Authorization, Cookie, X-API-Key, or similar)
 - HTTP request/response bodies or raw payloads
 - User-identifiable fields (email, name, user_id, ip_address, phone)
@@ -19,5 +21,6 @@ block safe. If there is a safe alternative, suggest it.
 
 ## Security — Error Handling
 
-Flag cases where errors are silently swallowed (empty `catch`, `.unwrap()` without
-context, `let _ = result`) in code paths that handle external input or network responses.
+Flag cases where errors are silently swallowed (empty `catch`, `.ok()` without
+handling, `let _ = result`) or where operations like `.unwrap()`/`.expect()` may panic,
+in code paths that handle external input or network responses.