Add household earnings sweep chart for bill review PRs

[PavelMakarchuk]

Summary

• New script scripts/generate_household_chart.py that generates a plotly chart showing net benefit by earnings for a representative household
• Auto-selects household archetype based on reform type (EITC, CTC, rate cuts, etc.)
• Uploads chart as an embedded image in PR comments via --upload-to-pr
• Integrated into /encode-bill workflow as Phase 5b (after compute_impacts, before PR creation)

How it works

1. Fetches reform_params + provisions from Supabase
2. Pattern-matches reform type → picks household (single parent + 2 kids for EITC/CTC, single filer for rate cuts, married couple for joint reforms)
3. Runs PE-US Simulation with axes to sweep employment income ($0 → max)
4. Generates plotly PNG + interactive HTML
5. Uploads PNG to charts branch via GitHub Contents API, embeds in PR comment

Example output

See PR #118 comment for a live example (CT SB69 — Eliminate State EITC).

CLI usage

python scripts/generate_household_chart.py --reform-id ct-hb5134
python scripts/generate_household_chart.py --reform-id ct-hb5134 --upload-to-pr 119
python scripts/generate_household_chart.py --reform-id va-hb979 --earnings-max 2000000

Test plan

• Verified against ct-hb5134 (CTC): flat $1,200 benefit up to $100k
• Verified against ok-hb2229 (EITC): triangle-shaped benefit curve
• Verified against ct-sb69 (EITC elimination): inverted EITC loss curve
• PR comment upload working on PR Bill review: Eliminate State EITC (CT) #118
• Test with rate cut reform (ga-sb168 blocked by PE-US version issue)
• Test with married couple archetype

🤖 Generated with Claude Code