Package rename populace_dynamics → microcosm_dynamics requires a design-binding repin ceremony

[MaxGhenis]

The 2026-08-07 product rename (Populace→Microcosm, Ledger→Chronicle) renamed this repo to microcosm-dynamics but deliberately left the code untouched (#372 has the minimal prose change). A full mechanical sweep was authored and run against the suite; results (150 failed, 44 errors) established the constraints any real rename must satisfy:

1. Never touch the registered evidence: docs/analysis/, docs/registrations/, runs/, data/external/, scripts/*_selector_config.json, benchmarks/registry.json — all byte-frozen with content hashes and fail-closed mutation tests.
2. "ledger" is repo vocabulary, not the product: selection_ledger_sha256, relabel_ledger, full_scenario_ledger, ref_ledger, qstar_ledger_sha256, docs/forecasts/timeline_ledger.json, estimates/ledgers.py etc. are generic bookkeeping terms inside registered keys. They stay.
3. Design bindings pin source paths and hashes: registered artifacts embed src/populace_dynamics/... module paths and tree shas. Renaming the package directory invalidates the bindings by construction — the rename must ship WITH a repin (the amendment-ratification repin flow, cf. Repin design binding to amendment-11 ratification (revision 13) #371) in the same change, plus updated schema-version/artifact-id constants only where the repin re-records them.
4. Dist name policyengine-social-security-model → microcosm-dynamics should ride the same repin.
5. Prose (README ✓, qmd chapters, ADR filenames) can rename freely where not hashed; the PDF at microcosm.institute/dynamics/paper regenerates from this repo afterward.

Owner: the dynamics lane (registered-analysis protocol), not a drive-by sweep.