chore(cleanup): drop dead utils::env_compat::read_env_either

Identical re-export of `read_env_with_legacy` with no callers
anywhere. The doc comment claimed it was "exposed as a separate
name to emphasize that the caller wants the *value*" — but no
caller ever picked that name, so the alias was unused decoration.

Workspace test sweep stays green (118 + 414 lib tests).

Assisted-by: Claude Code:claude-opus-4-7

Author: mikolalysenko

crates/socket-patch-core/src/utils/env_compat.rs

@@ -67,14 +67,6 @@ pub fn warn_legacy_once(legacy_name: &'static str, new_name: &'static str) {
 
 /// Read the new env var; if it isn't set, also probe the legacy name and
 /// surface a deprecation warning when the legacy name is set. Returns the
-/// new-name value when set, otherwise the legacy value (or `None`).
-///
-/// Same behavior as `read_env_with_legacy` but exposed as a separate name to
-/// emphasize that the caller wants the *value* and accepts either source.
-pub fn read_env_either(new_name: &'static str, legacy_name: &'static str) -> Option<String> {
-    read_env_with_legacy(new_name, legacy_name)
-}
-
 /// Renamed env vars whose legacy `SOCKET_PATCH_*` names are still honored.
 ///
 /// First entry of each tuple is the new name (what clap and current code