Fix Stage 12 comparison tolerance and UK geography metadata

[anth-volk]

Problem

Stage 12 result comparison currently reports immaterial floating-point differences, while UK report artifacts can omit constituency and local-authority names and coordinates when the canonical lookup files are not resolved.

Scope

• Compare numeric result values using an absolute tolerance of 0.01 while retaining exact artifact digests.
• Resolve UK constituency and local-authority names and coordinates from the canonical PolicyEngine UK lookup files.
• Fail explicitly when required lookup data or output values are missing.
• Verify that the Stage 12 service credentials can read the two required lookup objects without granting access to unrelated private dataset objects.
• Add unit tests and deployment-infrastructure validation for these behaviors.

Acceptance criteria

• Numeric values whose absolute difference is no greater than 0.01 compare as equal.
• Both Stage 12 child simulations receive valid UK geography output metadata.
• Missing geography lookup data causes an explicit failure.
• Automated tests cover the comparison and geography handlers.
• Deployment validation checks access to both canonical lookup objects.