Add the CHIP §71109 reform-coverage probe when the engine encodes it (pe-us#9346)

Split from #767. H.R.1 §71109 narrows CHIP alien eligibility on 2026-10-01 with the same qualified list as Medicaid, but policyengine-us 1.819.0 tests only ~UNDOCUMENTED in is_chip_eligible_child / is_chip_eligible_standard_pregnant_person — the model-side gap is PolicyEngine/policyengine-us#9346. No reform toggle can bind on the current lock, so #767 ships the data precondition (humanitarian-status children present and gated) without a CHIP probe.

When the pe-us version bump that lands #9346 happens (fold into the bump checklist):

1. Add a hr1_chip_humanitarian_eligibility_restoration probe to tools/build_us_release_input_coverage_manifest.py mirroring hr1_medicaid_humanitarian_eligibility_restoration — restore the pre-§71109 CHIP status list at 2027, budget measure per_capita_chip (or the CHIP cost variable the encoding uses), expected positive, binding through immigration_status_str, floor ~$5M — and regenerate the manifest.
2. Extend test_us_hr1_immigration_channels.py with the synthetic CHIP household (TPS/refugee child in a CHIP income band, takes_up_chip_if_eligible pinned).

The emitted humanitarian under-19 masses on the 2024 ASEC run (#767 design comment: TPS 120k, parole 102k, refugee 56k, asylee 59k weighted) are the data-side evidence the probe will have support.

Wait for the policyengine-us version bump containing #9346, then read tools/build_us_release_input_coverage_manifest.py and test_us_hr1_immigration_channels.py alongside the Medicaid probe. Add the CHIP probe and synthetic TPS/refugee household, regenerate the manifest, and confirm the probe is positive, binds through immigration_status_str, and clears the stated floor.