pi-guardrails v0.12.0

bd90cdf: Remove the permission gate command explainer and its subagent runtime.
5cef4eb: Split Guardrails into separate policy, path-access, and permission-gate extensions backed by shared config, generated JSON schema support, and refreshed README documentation.

Breaking: renamed public event bus events to guardrails:action:blocked, guardrails:risk:detected, guardrails:feature:request, and guardrails:feature:register. Blocked and risk events now use core Action and Safety payload shapes.

7b01ab4: Move config migrations into shared modules and only show onboarding when no guardrails config exists.
5d76145: Update settings utilities to the latest version.