gate: harden fail-closed delegation boundary

[RyshMan]

Problem

• delegation intent and boundary enforcement needed stronger fail-closed behavior so indirect execution paths cannot silently bypass policy checks
• pack and script intent surfaces needed regression coverage to keep the boundary deterministic across CLI, e2e, and acceptance flows
• docs and compatibility references needed to match the tightened contract

Changes

• harden delegation intent normalization and boundary evaluation in the gate path
• add CLI, core, scenario, acceptance, and e2e coverage for delegation-chain and script-intent fail-closed behavior
• update README and contract docs to reflect the stricter boundary behavior and test coverage expectations

Validation

• ./gait doctor --json
• make prepush-full
• repo pre-push hook on git push -u origin codex/adhoc-fail-closed-boundary-hardening

[chatgpt-codex-connector]

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