ACS-local donor worker count uses the earnings proxy because the support base drops A_LFSR #1554

After #779 (the #767 humanitarian immigration statuses), the US immigration kernel tests workers with measured labor-force status: A_LFSR in (1, 2, 3, 4) at age 16 or older (us_runtime/immigration.py, _CPS_LABOR_FORCE_STATUS_CODES). The ACS-local stage (us_runtime/acs_local_immigration.py) applies the same test to ACS rows by mapping ESR onto the A_LFSR codebook. It also measures the donor's delivered worker mass with that test, but only when the donor carries A_LFSR.

In production the donor does not carry it:

• tools/build_us_puf_support_base.py (_with_us_immigration_inputs_from_asec_source) attaches A_LFSR from the pinned ASEC archives as an ephemeral input, runs the immigration stage, and then drops the column from its output.
• tools/_legacy/build_us_acs_multispine_base.py reads that support base as the ACS-local donor.
• So _donor_status_masks falls back to the earnings pair (WSAL_VAL > 0 or SEMP_VAL > 0, or the harmonized income equivalents) on donor rows. The stage receipt records the test it used in donor_status_columns.worker.

Effect. The ACS worker residual (the 9.7M national control minus what the donor delivers at pooled weights) carries the gap between prior-year earnings and current labor-force status on donor rows. When the kernel bound the national control, it classified those same rows with A_LFSR. The ACS side and the kernel agree; only the donor's delivered count uses the proxy.

Fix options.

1. Restore A_LFSR on donor rows in the ACS multispine builder with fill_asec_labor_force_status_source, using the pinned archives the support base already uses (exact PERIDNUM join).
2. Keep A_LFSR, or a derived labor-force flag, on the support base output.

Once the donor carries A_LFSR, _donor_status_masks uses it with no further change. The earnings fallback can then become a refusal, so the two sides can never use different worker tests again.

Acceptance: an ACS-local staging receipt whose donor_status_columns.worker reads A_LFSR in [1, 2, 3, 4] and age >= 16, and a test that refuses a donor without A_LFSR.