s891.py

from research import *
s=begin(891,'Checkpoint the partial-action explanation','What does the60-action prefix add to the Strategy model?',{},['C832–890'])
prefix=[r for r in json.loads((ROOT/'journal.json').read_text()) if r['step']<=890]
body="""# Chronological families: checkpoint after C891

Sixty actions are complete in the current cycle.

The common model now explains complete list paths, File_52c paired inversions, the NT display and finite Key domains. Each comparison retains the information its operation needs: category, order, digit register, grid, anchor and source role.

The operator result is precise. A reduced p/q Key preserves hZ on hqZ. A staged word preserves it on h times the least common multiple of its reduced prefix denominators. Consequently equal final scalar products can have different admissible intermediate grids. Different held anchors create a separate constant placement displacement.

Whole-field tests matter: File46's outer920→1000 completion does not make all interior heads integral, and no common anchor can repair that. The five-row quarter-carrier family follows one divisor rule per Key. The authorized File51a civil-count chains satisfy the stagewise criterion; neighboring Rounded widths do not replace their inputs.

C850–858 and C859–870 passed independent source-based review. No second inversion, new probability tally, canonical edit or scope extension has been introduced.

Next: the complete six-pair twelvefold carrier lift, its endpoint-response field and the retained147-year terminal biography; then integrate the mechanisms into a reader-facing explanation.
"""
a=artifact('deliverables/490d_Chronological_Families_Checkpoint_C891.md',body)
finish(s,{'checkpoint':a,'prefix':len(prefix)},'The Key family is now explained as exact partial action on declared grids and anchored paths. The next whole-family test can distinguish outer expansion from retention of an internal biography.','Reconstruct the complete six-row macrohead field.',{'prefix59':len(prefix)==59,'last890':prefix[-1]['step']==890})