Define and gate pi-control 1.0 readiness

[ChefGroep]

pi-control is public and useful, but a 1.0 bump should reflect a stable contract rather than a cosmetic semver signal.

Proposed 1.0 gates:

• Tool schemas (pi_session, pi_model, pi_tool, pi_state, pi_verify) have documented compatibility expectations.
• State-changing actions have tests for failure/rollback or explicit non-rollback semantics.
• README examples match executable tool schemas.
• Package tarball + Pi manifest contract are checked in CI.
• CI badge/gates are stable on the supported Pi/Node matrix.
• Changelog/release policy exists and breaking changes require a major bump.
• Positioning versus pi-agent-control-extension is explicit.

Related: CHE-234.