feat(codex): redeem banked usage-limit resets via /usage reset (#64280)

OpenAI lets ChatGPT-plan Codex users bank rate-limit reset credits, but
until now they could only be redeemed from the Codex CLI/app or the
website. This wires the same backend API into Hermes:

- /usage on the openai-codex provider now shows "You have N resets
  banked - use /usage reset to activate" (parsed from the
  rate_limit_reset_credits field the /usage endpoint already returns).
- New /usage reset subcommand (CLI + gateway) redeems one banked
  credit via POST .../rate-limit-reset-credits/consume with a UUID
  idempotency key, mirroring codex-rs backend-client semantics
  (PathStyle /wham vs /api/codex, ChatGPT-Account-Id header,
  reset/nothing_to_reset/no_credit/already_redeemed outcomes).
- Guard: redemption is refused while no rate-limit window is fully
  exhausted, since a banked reset restores the FULL 5h + weekly
  allowance and spending it early wastes it. /usage reset --force
  overrides. Zero banked credits and non-codex providers are refused
  with clear messages; nothing_to_reset reports the credit was NOT
  spent.
- i18n: new gateway.usage.unknown_subcommand / reset_wrong_provider
  keys across all 16 locales; docs updated (cli.md, messaging index).

Tested with unit tests plus a real-socket E2E against a local fake
Codex backend exercising redeem/guard/force and the /usage hint.

hermes_cli/commands.py

@@ -228,7 +228,8 @@ COMMAND_REGISTRY: list[CommandDef] = [
     CommandDef("help", "Show available commands", "Info"),
     CommandDef("restart", "Gracefully restart the gateway after draining active runs", "Session",
                gateway_only=True),
-    CommandDef("usage", "Show token usage and rate limits for the current session", "Info"),
+    CommandDef("usage", "Show token usage and rate limits; `reset` redeems a banked Codex limit reset", "Info",
+               args_hint="[reset [--force]]"),
     CommandDef("credits", "Show Nous credit balance and top up", "Info"),
     CommandDef("billing", "Manage Nous terminal billing — buy credits, auto-reload, limits", "Info",
                cli_only=True),