Encode FY2027 SNAP COLA values when USDA publishes the memo (~August 2026)

USDA typically publishes SNAP fiscal-year COLAs in early August (https://www.fns.usda.gov/snap/allotment/COLA). When the FY2027 memo (effective 2026-10-01) is out, encode the official values following the FY2026 pattern (explicit dated values + memo reference, as in the `fy26` COLA entries):

- [ ] `parameters/gov/usda/snap/max_allotment.yaml` — explicit `2026-10-01` values per region and household size (the official numbers come from the June 2026 Thrifty Food Plan cost, so they will differ from our CPI-U-based projection)
- [ ] `parameters/gov/usda/snap/income/deductions/standard.yaml`
- [ ] `parameters/gov/usda/snap/income/deductions/excess_shelter_expense/cap.yaml`
- [ ] `parameters/gov/usda/snap/income/deductions/excess_shelter_expense/homeless/deduction.yaml`
- [ ] `parameters/gov/usda/snap/asset_test/limit.yaml` — if the memo changes the resource limits (7 U.S.C. 2014(g)(1) adjusts by CPI rounded down to the nearest $250, so they often hold flat)
- [ ] Utility allowances (`income/deductions/utility/`) — from the separate FY2027 SUA table release
- [ ] Recalibrate any tests pinning Oct–Dec 2026 / FY2027 values (including `tests/policy/baseline/partners/**`, which are gated — follow the partner-test protocol in `AGENTS.md`)

Notes:

- The minimum allotment derives from the 1-person maximum in the model, so no separate parameter update.
- While in `asset_test/limit.yaml`: its file-level `uprating: gov.usda.snap.uprating` metadata is currently inert (no `propagate_metadata_to_children`, and the values live under `standard`/`elderly_disabled` children) — the same silent-inert pattern #9059 fixes for California. Decide whether to delete it or make it live with the statutory $250-round-down; straight CPI uprating without rounding would overstate the limits.
- Until the memo lands, FY2027 values are CPI-U projections via `uprating.yaml` (see the refresh issue this one follows from).

Wait for the FY2027 USDA SNAP COLA memo and separate SUA table, then compare the FY2026 entries in parameters/gov/usda/snap/ with the listed files. Read AGENTS.md for the gated partner-test protocol and run the affected policy tests, including tests/policy/baseline/partners/**. Done means explicit 2026-10-01 values, memo references, updated utility allowances and tests, with asset limits handling the statutory $250 rounding correctly.

Written by the indexing model from the issue text.