Wire MiniMax-M2.7 and MiniMax-M2.7-highspeed into the model catalog,
CLI model picker, and agent auxiliary/metadata subsystems.

Changes:
- hermes_cli/models.py:
  - Add 'minimax-oauth' to _PROVIDER_MODELS with MiniMax-M2.7 and
    MiniMax-M2.7-highspeed
  - Add ProviderEntry('minimax-oauth', 'MiniMax (OAuth)', ...) to
    CANONICAL_PROVIDERS near existing minimax entries
  - Add aliases: minimax-portal, minimax-global, minimax_oauth in
    _PROVIDER_ALIASES
- hermes_cli/main.py:
  - Add 'minimax-oauth' to provider_labels dict
  - Insert 'minimax-oauth' into providers list in
    select_provider_and_model() near the other minimax entries
  - Add 'minimax-oauth' to --provider argparse choices
  - Add _model_flow_minimax_oauth() function: ensures login via
    _login_minimax_oauth(), resolves runtime credentials, prompts for
    model selection, saves model choice and config
  - Add dispatch elif branch for selected_provider == 'minimax-oauth'
- agent/auxiliary_client.py:
  - Add 'minimax-oauth': 'MiniMax-M2.7-highspeed' to
    _API_KEY_PROVIDER_AUX_MODELS
  - Add 'minimax-oauth' to _ANTHROPIC_COMPAT_PROVIDERS set
- agent/model_metadata.py:
  - Add 'minimax-oauth' to _PROVIDER_PREFIXES frozenset
  - MiniMax-M2.7 context length (200_000) already covered by the
    existing 'minimax' substring match in DEFAULT_CONTEXT_LENGTHS

Add and extend tests for the minimax-oauth provider across three test
modules.

New file: tests/test_minimax_oauth.py (15 tests)
  - test_pkce_pair_produces_valid_s256: verifies PKCE verifier/challenge
    pair produces a valid S256 hash and correct lengths
  - test_request_user_code_happy_path: mocks httpx, verifies correct
    POST parameters and response parsing
  - test_request_user_code_state_mismatch_raises: verifies CSRF guard
  - test_request_user_code_non_200_raises: verifies HTTP error handling
  - test_poll_token_pending_then_success: verifies polling loop retries
    on 'pending' and returns on 'success'
  - test_poll_token_error_raises: verifies 'error' status raises AuthError
  - test_poll_token_timeout_raises: verifies deadline expiry raises
  - test_refresh_skip_when_not_expired: verifies no HTTP call when token
    is fresh
  - test_refresh_updates_access_token: verifies new access/refresh tokens
    stored on successful refresh
  - test_refresh_reuse_triggers_relogin_required: verifies
    relogin_required=True on invalid_grant/refresh_token_reused
  - test_resolve_credentials_requires_login: verifies AuthError when no
    stored state
  - test_provider_registry_contains_minimax_oauth: PROVIDER_REGISTRY key
  - test_minimax_oauth_alias_resolves: portal/global/underscore aliases
  - test_get_minimax_oauth_auth_status_not_logged_in
  - test_get_minimax_oauth_auth_status_logged_in

Extended: tests/hermes_cli/test_runtime_provider_resolution.py
  - test_minimax_oauth_runtime_returns_anthropic_messages_mode
  - test_minimax_oauth_runtime_uses_inference_base_url

Extended: tests/hermes_cli/test_api_key_providers.py
  - TestMinimaxOAuthProvider class (8 tests) covering registry keys,
    auth_type, endpoints, client_id, aliases, CANONICAL_PROVIDERS
    listing, _PROVIDER_MODELS entries, and aux model

Add comprehensive documentation for the minimax-oauth provider.

New file: website/docs/guides/minimax-oauth.md
  - Overview table (provider ID, auth type, models, endpoints)
  - Quick start via 'hermes model'
  - Manual login via 'hermes auth add minimax-oauth'
  - --region global|cn flag reference
  - The PKCE OAuth flow explained step-by-step
  - hermes doctor output example
  - Configuration reference (config.yaml shape, region table, aliases)
  - Environment variables note: MINIMAX_API_KEY is NOT used by
    minimax-oauth (OAuth path uses browser login)
  - Models table with context length note
  - Troubleshooting section: expired token, timeout, state mismatch,
    headless/remote sessions, not logged in
  - Logout command

Updated: website/docs/getting-started/quickstart.md
  - Add MiniMax (OAuth) to provider picker table as the recommended
    path for users who want MiniMax models without an API key

Updated: website/docs/user-guide/configuration.md
  - Add 'minimax-oauth' to the auxiliary providers list
  - Add MiniMax OAuth tip callout in the providers section
  - Add minimax-oauth row to the provider table (auxiliary tasks)
  - Add MiniMax OAuth config.yaml example in Common Setups

Updated: website/docs/reference/environment-variables.md
  - Annotate MINIMAX_API_KEY, MINIMAX_BASE_URL, MINIMAX_CN_API_KEY,
    MINIMAX_CN_BASE_URL as NOT used by minimax-oauth
  - Add minimax-oauth to HERMES_INFERENCE_PROVIDER allowed values

Close integration gaps discovered by auditing qwen-oauth's file coverage.
These are surfaces the original salvage missed — they all existed on
main and were added in the 747 commits since PR #15203 was opened.

Coverage added:
- agent/credential_pool.py: seed pool from auth.json providers.minimax-oauth
  so `hermes auth list` reflects logged-in state and
  `hermes auth remove minimax-oauth <N>` works through the standard flow.
- agent/credential_sources.py: register RemovalStep for minimax-oauth
  with suppression-aware `_clear_auth_store_provider`.
- agent/models_dev.py: PROVIDER_TO_MODELS_DEV mapping (-> 'minimax' family).
- hermes_cli/providers.py: HermesOverlay entry (anthropic_messages transport,
  oauth_external auth_type, api.minimax.io/anthropic base).
- hermes_cli/model_normalize.py: add to _MATCHING_PREFIX_STRIP_PROVIDERS so
  `minimax-oauth/MiniMax-M2.7` in config.yaml gets correctly repaired.
- hermes_cli/status.py: render MiniMax OAuth block in `hermes doctor`
  (logged-in / region / expires_at / error).
- hermes_cli/web_server.py: register in OAUTH_PROVIDER_REGISTRY + dispatch
  branch in _resolve_provider_status so the dashboard auth page shows it.
- website/docs/integrations/providers.md: full 'MiniMax (OAuth)' section.
- website/docs/reference/cli-commands.md: --provider enum.
- website/docs/user-guide/features/fallback-providers.md: fallback table row.
- scripts/release.py AUTHOR_MAP: amanning3390 mapping (CI gate).