fix(core): resolve saved Workers AI account IDs

[pkyanam]

Issue for this PR

Closes #48404

Bug report: #48404

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Workers AI's catalog endpoint still contains ${CLOUDFLARE_ACCOUNT_ID} after /connect saves accountId, so the native resolver rejects it before sending a request. Substitute the saved account ID during OpenAI-compatible mapping and keep it out of provider request options.

Preserves explicit endpoints and environment-account precedence. Covers saved configuration, legacy metadata, provider settings, and canonical provider aliases.

How did you verify your code works?

• Regression test reproduced the initialization error before the change.
• Core resolver, native mapping, and Workers AI plugin tests: 74 passed.
• Core retry/incomplete-stream/malformed-tool tests: 20 passed.
• bun typecheck in packages/core passed.
• Live patched resolver request to Workers AI DeepSeek Flash 0731 succeeded with the account ID supplied only through credential configuration and the environment variable unset.

Screenshots / recordings

Not applicable; no UI changes.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[pkyanam]

The bug report is already open: #48404, created before this PR. The description includes Closes #48404 and now also the full issue URL.

This appears to be a false positive for the v2 target: the dev version of pr-standards.yml checks only closingIssuesReferences, whereas the v2 workflow already falls back to closing keywords in the PR body for non-default branches. Please keep this PR targeted at v2, as required by the current contribution guide.