Define and enforce critical-extension attenuation

[bordumb]

Finding

GrantRequest and GrantStatement carry CriticalExtensions, but neither the pre-signing author scope projection nor the production delegation attenuation kernel compares them.

The current gaps are visible in:

• auths_model::ScopeAuthorityView, which omits extensions
• auths_authority::AuthorityDimension, which has no extension dimension
• auths_authority::evaluate_author_scope_view, which therefore cannot reject extension drift before signing
• auths_authority::EffectiveAuthority / AuthorityStateView and evaluate_grant_view, which do not preserve or compare extensions during production verification

As a result, a child proposal can add, remove, or change critical-extension payloads without the planner identifying that semantic change as a widening/mismatch dimension. Whether a particular extension narrows or widens authority is extension-specific, so silently ignoring the field is not a safe generic rule.

Required resolution

• Define the target-V1 critical-extension delegation relation explicitly.
• Until extension-specific attenuation algebras exist, require exact canonical equality between parent and child critical-extension sets.
• Add an Extensions authority dimension and stable negative diagnostics.
• Carry extensions through accumulated effective authority and production attenuation checks.
• Update the executable attenuation algebra, Lean/refinement bridge, semantic identities, fixtures, and negative tests atomically.
• Ensure TypeScript/Python/other Full Workflow delegation APIs cannot bypass the native check.

Discovered during

AP-SPEC-027 / AP27-PR5 implementation audit.