v0.26.6

Changed

• Container image: unpin claude-agent-sdk floor. The 0.1.73-
  0.1.77 "regression" we suspected at 0.26.0 was actually the
  OAuth-bare-env auth bug in disguise (Anthropic rejecting
  sk-ant-oat01-… tokens passed without the full credentials.json
  context). 0.26.2 fixed the auth path; claude-agent-sdk==0.1.72
  was a workaround that's no longer necessary. Verified locally on
  2026-05-08: 0.1.77 round-trips a real SDK query() in 5s with a
  bind-mounted credentials.json, no is_error=True/subtype=success
  failure. Back to claude-agent-sdk>=0.1.0.