hardening: steps 1-3 validation + sampler integrity + persona consistency

[RandomOscillations]

Summary

Hardening pass for Extropy pipeline steps 1-3 (spec/scenario/sample) plus persona consistency improvements.

This PR is for merge coordination and visibility. It intentionally keeps issues open until integration verification is complete.

Detailed handoff doc:

• /Users/adithyasrinivasan/Projects/extropy/docs/branch-notes/steps1-3-hardening.md

What Changed

• Scenario validator now resolves both base population and extended attributes.
• Scenario condition literals are validated against categorical option domains.
• extropy validate now has robust spec-type detection and persona validation path.
• Sampler now reconciles household-derived fields after assignment.
• Partner correlation moved to policy/metadata-driven resolution with legacy fallback.
• Semantic validator now flags ambiguous modifier overlaps and partner-policy gaps.
• Sampling now surfaces modifier condition-eval failures (strict/permissive modes).
• Sampling now enforces expression constraints by default (without --skip-validation).
• Persona renderer applies semantic context to avoid employment/occupation contradictions.

Related Issues (kept open)

Relates to: #110, #113, #114, #117, #118, #119, #120, #121, #122, #123

Merge Notes

• This branch increases strictness; older specs may fail faster.
• Keep issues open until merged + verified on integration runs.