v0.2.6

Fixed

• Default-allow ANTHROPIC_* env vars without project burrow.toml [env]
  (burrow-e9e7). A fresh project clone with no burrow.toml started
  claude-code inside the sandbox with an empty env block, so
  ANTHROPIC_API_KEY / ANTHROPIC_AUTH_TOKEN / ANTHROPIC_BASE_URL /
  CLAUDE_CODE_OAUTH_TOKEN set on the burrow process never reached the
  agent — the CLI then errored on first call. New optional
  AgentRuntime.envPassthrough lets a built-in runtime declare the host
  env names its CLI consults at startup; runUpCommand unions every
  effective agent's envPassthrough (skipping agents with
  forwardCredentials = false) onto SandboxProfile.envPassthrough, so
  the runtime's intrinsic env contract no longer requires a per-project
  [env] block. claude-code declares the four names above. Per-project
  keys (DATABASE_URL etc.) still belong in burrow.toml [env].