chore: improve expired login error

[Cedric / ViaDézo1er (viadezo1er)]

Before:

❯ BRAINTRUST_API_KEY=sk-invalid-key bt topics
error: API error (401): Invalid API Key [timestamp=1781231940.159] [request_id=sfo1::z24tx-1781231940049-e052d7bd3099]

After:

❯ BRAINTRUST_API_KEY=sk-invalid-key bt topics
error: API error (401): Invalid API Key [timestamp=1781232168.898] [request_id=sfo1::m7gcb-1781232168809-b59697fa5830]
Your credentials may be expired or invalid. Re-authenticate with `bt auth login`, or run `bt auth profiles` and `bt status` to check profile status.

For stale refresh OAuth tokens:

❯ bt topics --profile delete-this
error: oauth refresh token expired or was rejected for profile 'delete-this' (Refresh failed - please re-authenticate); re-run `bt auth login --oauth --profile delete-this`

[github-actions]

Latest downloadable build artifacts for this PR commit 4606a84d858e:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/27391691695
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