chore: remove Lean spec; ADRs are the single source of truth

The spec/ Lean semantic master had no conformance gate, no codegen, and
no CI tie to implementations — alignment was carried entirely by human
review, the same mechanism that carries the ADRs. In practice the ADRs
plus greppable code comments were already the load-bearing artifacts,
so spec/ was the most expensive kind of stale documentation.

- delete spec/ and the spec-check CI workflow
- README: constitution rewritten around ADRs as decision truth
- AGENTS.md/CLAUDE.md: discipline re-anchored (new decisions -> new ADR,
  never rewrite ADR history; supersede instead)
- code comments: re-anchor 'Mirrors Spec.X' invariants to ADR numbers
  (cph-diag, cph-check, cph-model, hub runner/capacity/org, prisma)
- leave ADR bodies and .scratch audit snapshots untouched (history);
  fix live references in open readiness tickets

hub/src/capacity/dimensions.ts

@@ -1,6 +1,6 @@
 /**
- * ADR-0022 capacity dimensions (spec `Spec.System.Capacity.CapacityDimension`).
- * The 23 PINNED dimensions; exact numeric ceilings are `OPEN` and calibrated by
+ * ADR-0022 capacity dimensions.
+ * The 23 pinned dimensions; exact numeric ceilings are open and calibrated by
  * capacity testing. This module is the single source of the dimension set shared
  * by the platform-ceiling config and the org capacity-policy service.
  */