Replaces blind tree.sync() on every Discord reconnect with a diff-based
reconcile. In safe mode (default), fetch existing global commands,
compare desired vs existing payloads, skip unchanged, PATCH changed,
recreate when non-patchable metadata differs, POST missing, and delete
stale commands one-by-one. Keeps 'bulk' for legacy behavior and 'off'
to skip startup sync entirely.
Fixes restart-heavy workflows that burn Discord's command write budget
and can surface 429s when iterating on native slash commands.
Env var: DISCORD_COMMAND_SYNC_POLICY (safe|bulk|off), default 'safe'.
Co-authored-by: Codex <codex@openai.invalid>