#13484: feat(auth): restore Claude Code CLI OAuth credential sync

Re-adds Claude Code CLI integration that was removed in upstream commit 526303d9a. This restores the ability to authenticate using an existing Claude Code subscription (Claude Pro/Max) instead of manually pasting setup-tokens. Changes: - Re-add Claude CLI credential sync in external-cli-sync.ts - Re-add bidirectional token refresh write-back in oauth.ts - Re-add "Claude Code CLI" auth option in onboarding UI - Re-add claude-cli auth handler in auth-choice.apply.anthropic.ts - Remove claude-cli deprecation warning in doctor-auth.ts - Pass allowKeychainPrompt options through store.ts <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR restores Claude Code CLI credential syncing for Anthropic auth by: - syncing Claude CLI credentials into the auth profile store on load (`external-cli-sync.ts` / `store.ts`) - writing refreshed Anthropic OAuth credentials back into Claude CLI storage during token refresh (`oauth.ts`) - exposing a new onboarding auth choice (`claude-cli`) and updating hints in the auth-choice UI - removing the prior “Claude CLI is deprecated” doctor warning Key integration points are the auth store load/sync layer and the OAuth refresh path; both now interact with `cli-credentials.ts` for reading/writing Claude CLI credentials. <h3>Confidence Score: 2/5</h3> - Not safe to merge as-is due to a confirmed doctor-flow regression and likely macOS Keychain prompt behavior in non-auth commands. - The doctor deprecated-profile removal logic is internally inconsistent (and contradicts its unit test), and the auth store load path can trigger Keychain prompts unexpectedly on macOS because `allowKeychainPrompt` isn’t plumbed through `loadAuthProfileStore()`. Both are concrete, user-visible issues that should be fixed before merge. - src/commands/doctor-auth.ts, src/agents/auth-profiles/store.ts <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->