Update API partner contract tests to match live partner traffic

[hua7450]

Summary

Reworks the partner API contract test suite (policyengine_us/tests/policy/baseline/partners/**) so fixtures mirror what partners actually send, verified against 5,415 live /us/calculate requests (7 days ending 2026-07-04) from the household API analytics database.

Closes #8588

Fixture wiring fixes

• state_code_str input does not backfill state_code, so enum readers evaluate under the California default #8887 geography: state_code_str does not backfill the state_code enum (default CA), so every enum reader (CHIP per-capita chain, SNAP utility region/SUA, ACA benchmarks via geography) evaluated as California. Edge-case fixtures now set the state_code enum. Signature replays keep each partner's observed geography key — including state_code_str where partners really send it, faithfully pinning current production behavior.
• YAML fixtures set employment_income (derived) instead of employment_income_before_lsr (input) — TANF sees $0 earnings #8802 derived inputs: the YAML runner does not backfill the five LSR-derived inputs the way the API's Python Simulation wrapper does. Migrate partner fixtures to employment_income_before_lsr input #8920 (merged) migrated the employment_income keys suite-wide; this PR completes the set (self_employment_income, sstb_self_employment_income, weekly_hours_worked, long_term_capital_gains → their *_before_lsr/*_before_response forms). No partner fixture sets any LSR-derived input directly anymore.

Changes by area

1. Louisiana removed (10 files, 34 cases) — no partner sends Louisiana households.
2. Kansas added (26 cases, 6 files) — observed ks_tanf probes in live traffic; county payment groups, income/resource boundaries, KEESM 6220 child-support split, non-expansion Medicaid gap.
3. Federal edge cases reworked (395 → 316 cases) — zero-benefit-only suites replaced with parameter-derived positive and boundary pins (first real pins for CHIP per-capita amounts, Lifeline, housing assistance, MSP SLMB/QI, EITC phase-in, CTC refundable cap); ~122 duplicate state-variant cases pruned; all-zero artifacts converted by adding the partner-sent inputs that were missing.
4. State edge cases reworked (all 8 partner states, 210 cases) — same policies; stale non-binding boundaries re-anchored to 2026 uprated parameters. New traffic-driven coverage: tx/ceap.yaml (tx_ceap requested ~370/wk with zero coverage), wa/apple_health.yaml (~158/wk), and one lean case per Amplifi expansion county (Contra Costa, San Mateo, Santa Clara, Marin, Orange).
5. Signature replays fixed (all 9 files) — MyFriendBen replays were generated without any geography key, so all 34 cases evaluated as California and pinned $0 for every state program; real traffic sends state_code on 100% of state-output requests. Also swapped capital_gains for the long_term_capital_gains key partners actually send.

Partner-facing value corrections (signature replays)

Re-pinned values reflect what the API returns when the fixture geography matches the request:

What moved	Old (CA-default)	New
il_tanf (4 signatures)	$0	$11,319 (Cook County payment level, whole-dollar floored)
ma_tafdc	$0	$13,516
co_tanf	$0	$8,136
nc_scca_maximum_payment	$0	$16,932 (Wake County market rates)
wa_working_families_tax_credit	$0	$1,017.55
aca_ptc (TX signature)	$27,263.95	$13,734.22 (Dallas rating area, was CA benchmark)
lifeline (non-CA states)	$228	$111 federal-only ($153 TX) — $228 included CA's state add-on

Each headline amount was hand-derived from state parameters (derivations in YAML comments).

Coordination with main (merged through 2026-07-06)

Main was merged twice; conflicting upstream re-pins of the pre-rework fixture layouts were superseded by the reworked files, then all values re-pinned against the merged model:

• Fix CTC value and EITC disabled dependent child count #8895 ctc_value formula fix — 45 assertions (zero-liability families now show the refundable cap, e.g. 4,400 → 3,400)
• Update Colorado SSI supplement standards for 2026 #8807 Colorado 2026 OAP/AND-CS standards — 4 assertions (OAP $1,032/mo; AND-CS $994/mo now exactly ties the 2026 SSI FBR)
• Add county-level HUD utility allowance schedules for Texas and Kansas #8819 LA County LACDA FY2025 utility allowance — 1 assertion
• Fix MA TAFDC income-test boundary and IL TANF minimum payment #8918 IL TANF whole-dollar flooring + $1 minimum — 10 assertions (partial-year case is exactly 7×493 + 3×513 = 4,990)
• Migrate partner fixtures to employment_income_before_lsr input #8920 upstream employment_income migration — absorbed; this PR contributes the remaining derived-input keys

Not changed (follow-ups)

• amplifi/, impactica/, my_friend_ben/ named fixtures keep their observed shapes (only mechanical key renames from Migrate partner fixtures to employment_income_before_lsr input #8920 plus the two zero-valued self-employment keys here); geography/gains-key fidelity review tracked in Update API partner contract tests #8588.
• The model-side state_code_str input does not backfill state_code, so enum readers evaluate under the California default #8887 fix (backfilling state_code from state_code_str in system.py) is a separate, partner-facing behavior change.

Test plan

• Full partners suite passes locally against merged main: 628 cases
• CI passes

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