fix(consolidation): P2 savant B1 (Spd3 import) + G1 (OgitSchema alias)

P2 codex savant returned SHIP-WITH-FOLLOWUPS. Two 10-min nudges applied:

- B1: pillar/ewa_sandwich_3d.rs now imports Spd3 from linalg::Spd3 (was
  splat3d::spd3::Spd3, inconsistent with the rest of the sprint after
  fb925de standardized on linalg::Spd3). sandwich() stays from splat3d::spd3
  since that's still the canonical impl.

- G1: added pub type OgitSchema = schema::OntologySchema; alias to
  ogit_bridge/mod.rs for PR-X9 design doc compatibility (the design
  references OgitSchema 7×; PR-X13 implementation ships OntologySchema).
  Zero-cost rename via type alias.

Deferred to follow-on sweep (per PP-15 + P2 savant joint guidance):
- C3: SIMD-disambiguation prose on 12 compute-heavy free fns
- F2: 15 #![allow(missing_docs)] suppressions tighten
- A1: eig_sym_3 signature normalization (&Spd3 instead of &[[f32;3];3])
- G2: CognitiveBridge::nearest_basin arity vs PR-X9 design doc

These need carrier-shape decisions (Tensor1/Tensor2/Tensor4 newtype
choice) — savants agree this is a 1-2 day follow-on, not same-day patch.

P2 savant verdict persisted at .claude/knowledge/pr-consolidation-p2-savant-review.md.

Author: claude