New arborist.pi_star/ namespace centralizes canonical projections
under a name@version registry. Two existing canonicalizers re-homed
as registered π*'s:
- wikitext-base@v1 wraps arborist.wikitext.to_base
- claim-lattice@v1 wraps arborist.qa.parse_claims.parse_pointer_claims
Four stubs registered for follow-up modality tickets:
code-py-ast@v1, logic-kernel@v1, time-series-quantized@v1,
tabular-pinned@v1 — each raises NotImplementedError with a pointer
to ticket #000015.
Composition algebra in compose.py: PiStarComposition exposes
outer ∘ inner as a first-class π* with its own registry key
(default "<inner-name>-then-<outer-name>@v1"). canonical_composition_id
returns a SHA-256 fingerprint suitable for governance hash inclusion.
Order-sensitive: a∘b ≠ b∘a → different fingerprints.
Documentation: docs/pi-star-composition.md covers the rule (type-
compatible, deterministic, equivalence-class preserving), lossy vs
invertible compositions, worked text→claim-lattice example,
cross-domain anchor projections (future), authoring checklist.
Re-home is non-breaking: arborist.wikitext.to_base remains importable.
Tests: tests/test_pi_star.py (19 cases). Full suite: 1059 passed,
36 skipped.
