Bump spm-calculator to >=0.2.1 for Betson equivalence scale fix (#771)

`policyengine_us_data/utils/spm.py` already consumes `spm-calculator`
for base thresholds and the equivalence scale, but the dependency
range was pinned at `>=0.1.0` so the lockfile resolved to
`spm-calculator==0.1.0` -- which shipped a buggy linear OECD-modified
equivalence scale (reference family raw = 2.1) instead of the Betson
three-parameter scale with the 0.7 exponent (reference family raw =
3**0.7 approx 2.158) that BLS Garner (2021) documents and that
Census uses in its published SPM thresholds.

Version 0.2.0 of `spm-calculator` replaced the scale with the correct
Betson form; 0.2.1 then tightened the (shadow) CE recomputation path
toward BLS methodology (annualization, survey weights, mortgage
principal, internet services, modern CUTENURE split). Bumping to
`>=0.2.1` picks up both.

Impact on computed SPM thresholds (CPS input pipeline, unchanged
code, dependency bump only)
- 2 adult / 2 child reference family: unchanged (normalization
  anchor).
- 1 adult / 2 child owner-with-mortgage: $29,767 -> $32,437 (+9.0%).
- 2 adult / 0 child owner-with-mortgage: $27,906 -> $25,530 (-8.5%).
- Direction: single-parent-with-children units shift higher, larger
  childless-adult units shift lower -- matching the well-known Betson
  economies-of-scale properties.

This changes the SPM thresholds that `cps.py` writes onto the CPS
input dataset, which feeds every downstream SPM-based calibration
target and poverty classification. The update is a correctness fix,
not a policy change.

Validation
- All 714 unit tests pass (`uv run pytest tests/unit/`).
- `calculate_spm_thresholds_with_geoadj` output verified by hand
  against Betson math for 1A2C / 2A2C / 2A0C at owner-with-mortgage.
- Public API of `policyengine_us_data/utils/spm.py` unchanged across
  the version bump; no call-site updates required in `cps.py` or
  `calibration_utils.py`.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: MaxGhenis

changelog.d/migrate-utils-spm-to-spm-calculator.fixed.md

@@ -0,0 +1 @@
+Bump `spm-calculator` dependency from `>=0.1.0` to `>=0.2.1` so the SPM thresholds computed for the CPS input dataset use the Betson three-parameter equivalence scale (with the 0.7 exponent) published by Census, not the linear OECD-modified scale shipped in `spm-calculator==0.1.0`. Also picks up tenure-specific GEOADJ shares (renter 0.443, owner-with-mortgage 0.434, owner-without-mortgage 0.323) and the BLS-fidelity improvements in the CE recomputation path. For a 2-adult 2-child reference family the threshold is unchanged; non-reference families shift materially (1 adult / 2 children owner-with-mortgage: $29,767 -> $32,437, +9.0%; 2 adults / 0 children owner-with-mortgage: $27,906 -> $25,530, -8.5%). No code changes in `policyengine_us_data/utils/spm.py`; the package-level API is unchanged across the version bump.

pyproject.toml

@@ -42,7 +42,7 @@ dependencies = [
     "sqlalchemy>=2.0.41",
     "sqlmodel>=0.0.24",
     "xlrd>=2.0.2",
-    "spm-calculator>=0.1.0",
+    "spm-calculator>=0.2.1",
     "tenacity>=8.0.0",
 ]