Bug: Sampler does not reconcile marital_status / household_size after household assignment #114

Summary

The population sampler assigns partners via households.py but does not reconcile marital_status or household_size afterward. These attributes are sampled independently from the spec's distributions before household pairing occurs, leading to contradictions.

Evidence (from ASI Announcement study, 5,000 agents)

• 896 agents have marital_status = 'Single' but a non-null partner_id
• 1,114 agents have household_size = 1 but a non-null partner_id
• 78 married/divorced teenagers (age 18-19)
• 25 agents with Graduate Degree under age 22
• 86 retired agents under age 50

Root Cause

In extropy/population/sampler/core.py, the sampling loop processes attributes in topological order based on depends_on. marital_status depends on [age] and household_size depends on [marital_status, age]. Both are sampled from their distributions with age-based modifiers.

Then households.py pairs agents into partner relationships and assigns dependents — but it never updates the already-sampled marital_status or household_size to reflect the actual household structure.

Expected Behavior

After household assignment:

• Agents with a partner_id should have marital_status in {'Married', 'Domestic Partner'} (not 'Single')
• household_size should reflect the actual household membership count (at minimum >= 2 if partnered)
• Age-implausible combinations (married teen, retired 30-year-old) should be filtered or reconciled

Suggested Fix

Add a post-household reconciliation step in the sampler that:

1. Sets marital_status = 'Married' for all agents with a partner_id and marital_status = 'Single'
2. Recomputes household_size based on actual household membership
3. Optionally: validates age-plausibility constraints (no married under-18, no grad degrees under 22, etc.)