v0.26.3

Fixed

• In-container _provision_auth() now prefers the bind-mounted
  ~/.claude/.credentials.json over ANTHROPIC_API_KEY. When both
  are present (the 0.26.2 path), the SDK was picking the env var
  and getting rejected because Anthropic doesn't accept
  sk-ant-oat01-… OAuth tokens via bare env. The runner now
  unsets ANTHROPIC_API_KEY when credentials.json is mounted so
  the SDK uses the file-based credentials_file flow exclusively.
  This requires rebuilding the runner image (0.26.3).