Detect flat history and refuse it with exit 2; the legacy capability (rulings 82, 97) #145

Issue 2 of ledger/prd/namespace-independence-prd.md §6, opened on the principal's instruction (session ledger/sessions/2026-10-namespace-layout-authority.md).

Cites. PRD §3.1.1 (History written in the flat layout), §3.5.7 (What git still does).

Size. M. Depends on. Issue 1.

Appendix C note. Yes: spec v1.9.

Rulings carried. 82 (reading the flat layout in history is a legacy capability outside the verifier profile; a verifier without it refuses pre-v1.9 history), 97 (ruling 82 stands; the capability shrinks to L007, L009 and the base overlay).

What it builds. Before reading history, one path-limited query looks for the flat paths (.decisions/log, .decisions/roles, .decisions/sig) on the first-parent history of the verified commit and, when given, the base. A verifier without the legacy capability refuses such a repository with exit status 2, naming the first flat commit, and never reports it conformant. With the capability, history is read at both path patterns, told apart by path, and only its files' entities: landing keyed by entity across both patterns for L007 (with ruling 58's format: comparison), L009's pickaxe over both paths, and the base overlay reading a flat base. No flat semantics are read from history. Landing positions still decide authority verdicts until issue 12, and read only per-namespace paths; this is sound only because no committed store with flat history holds an authority record (confirmed by scan). Protocol: LP-3.35 (new), LP-8.30's re-layout exception, Appendix B row and Appendix C note.

Acceptance criteria (§4.1).

• AC-82. With the legacy capability, this repository's history, re-laid out in one commit, verifies with every entity's L009 author and immutability verdict the same as before the re-layout; there are no landing indexes to compare (85). Without it, the same repository is refused with exit 2, naming the first flat commit, and is never reported conformant (97).