* fix(ai): remove global process.env.ANTHROPIC_API_KEY deletion
The code was deleting process.env.ANTHROPIC_API_KEY to prevent the SDK
from using it when OAuth tokens were provided. However, this was a global
mutation that affected the entire Node.js process, causing the API key to
be unavailable after the first prompt.
The Anthropic SDK constructor already handles credential selection via
parameters (apiKey: null, authToken: token for OAuth vs apiKey: key for
regular keys), so the environment variable deletion was unnecessary.
* Update CHANGELOG.md for API key fix
a248e2547a