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- Derive PartialOrd+Ord on PileType and sort pile entries in pile_map_serde before serializing so save-file output is deterministic (M-4) - Add #[serde(skip)] to undo_stack so transient undo history is never written to save files, eliminating unnecessary bloat (M-3) - Add merge_at() accepting an explicit resolved_at timestamp so callers can inject the server-side time; merge() wraps it with Utc::now() for backwards compatibility (M-1) - Fix url_encode to percent-encode UTF-8 bytes rather than Unicode codepoints so multi-byte characters produce RFC 3986-compliant output (M-2) Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>