fix(anthropic): use platform.claude.com for OAuth token exchange

[ThinkCode]

Summary

hermes auth add anthropic --type oauth fails at the token-exchange step with:

Token exchange failed: HTTP Error 404: Not Found
Anthropic OAuth login did not return credentials.

Root cause

run_hermes_oauth_login_pure() in agent/anthropic_adapter.py POSTs the authorization code to https://console.anthropic.com/v1/oauth/token (_OAUTH_TOKEN_URL). Anthropic has retired that endpoint — it now returns HTTP 404. The browser authorize step and PKCE/state validation all succeed; only the exchange fails.

Notably, the token refresh path (refresh_anthropic_oauth_pure) was already updated to try platform.claude.com first with the console host as fallback. The login exchange was missed.

Fix

Make the login token exchange try https://platform.claude.com/v1/oauth/token first, falling back to the legacy console host — mirroring the existing refresh logic. If all endpoints fail, the last error is surfaced as before.

Test plan

• Reproduced the 404 on the old single-endpoint path
• With the fix, hermes auth add anthropic --type oauth completes: Added anthropic OAuth credential, and hermes auth status anthropic reports logged in
• Lint clean

[alt-glitch]

Duplicate of #48957 — both patch run_hermes_oauth_login_pure() in agent/anthropic_adapter.py with the identical mechanism: replace the single bare _OAUTH_TOKEN_URL POST with a token_endpoints = ["https://platform.claude.com/v1/oauth/token", _OAUTH_TOKEN_URL] list, loop with try/except, and raise the last error if all endpoints fail. #48957 (artemprudenkous90-sv) was opened earlier (2026-06-19) and is still open, so it's the canonical version.

Related bug reports: #47692, #45250. (Earlier same-fix attempts #47474, #47333, #46251, #45441, #46769 are all closed.)

[teknium1]

Closing as a duplicate. This was fixed via #51723 (salvage of #48706 by @yusekiotacode, which fixed both the CLI login and dashboard OAuth paths). Thanks for the report and the fix — credited in the cluster.

#51723