Add Belgian benefit administration facts

[MaxGhenis]

Summary

• add the SFPD January 2025 GRAPA regular-payment snapshot: beneficiary count, paid amount, and published sex partitions
• add exact December 2025 administrative child-benefit observations from Opgroeien, Iriscare, and Ostbelgien
• add the eight exact December 2023 Walloon parliamentary-response partitions without constructing an unpublished total
• correct the legacy Opgroeien package from NUTS1 Flanders to the Groeipakket administrative-scheme scope
• add source-package validation and regression coverage for Belgium scheme scopes

These are publisher facts with provenance only. They do not assert legal eligibility, participation rates, take-up behavior, calibration mappings, or simulator concepts.

Scope semantics

Opgroeien, Iriscare, Ostbelgien, and the Walloon response describe administrative scheme populations. They are not relabeled as Belgian or NUTS1 population totals. Downstream model layers must supply an explicit typed scheme-to-population mapping before using them as calibration targets.

The Opgroeien and Iriscare dashboard captures are pinned to the exact source bytes used for extraction. The SFPD and Walloon records retain their official source documents and selectors.

Validation

• both source-package validators pass
• 41 focused Belgium tests pass
• Ruff passes
• independent review found no actionable findings
• the full suite reached 745 passed and 1 skipped before stopping only on the old bundle-count fixture
• after updating the exact bundle census, uv run pytest -q tests/test_chronicle_bundle.py passes: 9 passed

Companion

PolicyEngine/microcosm#824 consumes only the GRAPA reference and intentionally leaves the child-scheme facts unbound until typed scheme-population support exists.