Armenia (am) spec-only country package: engine-free pool-reweight contract (#814)

[MaxGhenis]

Closes nothing; first implementation PR for #814.

What this adds

The Armenia (am/) spec-only country package — the third greenfield country after Belgium and the NZ plan — as a declarative contract only: an engine-free, NZ-style pool reweight of a pre-built, to-be-authenticated populace-us support artifact against public Armenian margins referenced from a future ledger-am.

• am/ package: country_package.json, source_stages.json, target_references.json (8 solver-eligible references across demography, household structure, consumption, labour, earnings, pensions, family benefit — Ledger references only, zero embedded values), gates.json (11 release-blocking gates, BE greenfield posture, no parity gates — no incumbent exists), geography_spine.json + release_contract.json (populace_am_{year}.h5, public boundary — ILCS and all target sources are openly disseminated by ArmStat), and the spec/ bundle (sources, catalogs, vintages, geography, spine).
• spec_engine/resolver.py: registers the Armenia kernel ids (load_populace_us_support_pool, assign_am_marz, clone_assign_communities, am_community_geography_gate) in F0_CONTRACT_ONLY_KERNEL_IDS, mirroring the BE registration — contract-only vocabulary, never presented as executable producer kernels.
• Tests: tests/golden/am_country_spec.json golden, test_spec_only_country_packages.py coverage for am/, activation-boundary contracts in test_country_spec.py (runtime activation is forbidden while any table-level harvest placeholder stands in for multiple source cells).
• docs/armenia-country-package-814/: HARVEST.md — the Chronicle/ledger-am handoff contract (per-fact provenance requirements; stale-value quarantines, e.g. the Jan-2022 pensioner count is marked evidence-not-target; a no-cross-currency doctrine — no US amount reaches an AMD margin through implicit exchange-rate multiplication) — plus NOTES.md (decisions and BE deviations) and the planning journal.

Provenance posture

Every donor record remains a US support record; per-record support-stratum and donor-country provenance must survive calibration and release, and nothing downstream may describe them as Armenian microdata. Geography is the 2022-census system (10 marzes + Yerevan; 71 consolidated communities post-amalgamation) with no invented community list — assignment is uniform within the target-assigned marz pending the community-distribution harvest. No support_spine.json is declared because the current shared schema would falsely describe this package's input as raw-ASEC construction; authentication of the donor artifact belongs to the source contract.

Verification

• uv run pytest packages/microcosm-build: 6,556 passed, 45 skipped, 0 failed (locked env with policyengine-us==1.819.0). An independent pre-push re-run without the us extra tripped three test_us_release_head_to_head_scorer.py tests (untouched by this branch); all 16 pass once the extra is synced — they appear to run rather than skip when the US engine is absent, a pre-existing marker-guard gap, noted here rather than fixed.
• Focused package/golden/compiler suite: 101 passed. Shared-spec: 1,334 passed, 42 skipped.
• ruff check, tools/ci_test_groups.py --verify, git diff --check: clean.
• Changelog entry: changelog.d/814-armenia-country-package.added.md.

Not in this PR (tracked on #814)

ledger-am fact packages (the demographic core is already harvested with sha256 provenance from the ArmStat statbank API — census-2022 population by marz × sex verified against the official 2,932,731 total), the shared geography/source-coverage runtime generalizations (#263/#265 lineage), the calibration run, and the rules leg (TheAxiomFoundation/rulespec-am, corpus-first, content-free until an am-rulespec-* release exists).

Open questions for maintainer review are listed at the top of NOTES.md — the sharpest one: which immutable populace-us artifact + licence is authoritative for the donor pool.

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