agent-shell-py 0.3.1

Isolation policy environment configuration

AgentShell can now select its isolation policy through the process environment:

export AGENTSHELL_ISOLATION_POLICY=linux-pid-namespace

Accepted values are none and linux-pid-namespace. Resolution is deliberately predictable:

1. An explicit isolation_policy= object
2. AGENTSHELL_ISOLATION_POLICY
3. NoIsolation()

Empty or unknown values raise ValueError instead of silently disabling isolation. When the
variable is unset, existing callers retain the NativeExecutionHost() plus NoIsolation()
default.

Verification

• Added public-constructor coverage for both values, invalid configuration, the unchanged default,
  and explicit-policy precedence.
• Added a real-process integration test proving the environment-selected CLI runs as PID 2 inside
  the Linux PID namespace.
• Updated the README, architecture documentation, and invoking-cli-agents skill/API reference.
• All 860 unit and integration tests passed locally and in GitHub Actions.
• Independent Claude Code Opus review at high effort returned READY TO COMMIT with no actionable
  warnings.

Full changelog: v0.3.0...v0.3.1