…osine helper for FALSIFY-CPU-GPU-005 part b (#1441)

Canonical record of today's split-track cycle (PRs #1438-#1440).
Maintains the §41/§42 amendment cadence — each /loop iteration that
lands ≥3 PRs gets a single audit story.

Chain landed:
- #1438: FALSIFY-APR-DISTILL-TRAIN-005 PARTIAL_ALGORITHM_LEVEL
  (precompute byte-determinism, 2 unit tests, local + remote-stub
  branches)
- #1439: FALSIFY-APR-DISTILL-TRAIN-006 PARTIAL_ALGORITHM_LEVEL
  (train cache-resume idempotency, 2 unit tests, negative + positive
  halves)
- #1440: cpu_vs_gpu_cosine_similarity helper at module scope + 3 tests
  (parallel=1, orthogonal=0, fail-closed; cosine math now callable
  without --features cuda for the future part b wgpu cosine gate)

§43 documents: what landed (table), coverage flips (TRAIN-005, TRAIN-006
unbound → PARTIAL_ALGORITHM_LEVEL), why for MODEL-1+MODEL-2 (parallel
contract drift closure + part b infrastructure), Five Whys, ship %
effects (MODEL-1 87→88, MODEL-2 54→56), and next-session pickup
options (CPU-GPU-005 part b OR distill-train real implementation).

Coverage tally: 15+33 → 15+35 (+2 PARTIAL_ALGORITHM_LEVEL closed).

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

…VEL + TRAIN-009 BLOCKER_FIXTURE_ABSENT (#1443)

Closes the last three contract drifts in apr-cli-distill-train-v1
(tasks #218 + #247 claimed PARTIAL but YAML had no algorithm_evidence
blocks). Same fix-pattern as TRAIN-005/006 (PRs #1438, #1439).

TRAIN-007 (pv validate exits 0) — PARTIAL_ALGORITHM_LEVEL
  Live verification 2026-05-04 on this branch: pv validate exits 0
  with "0 error(s), 0 warning(s)". Meta-discharge via the pre-commit
  hook + manual operator runs that have validated every amendment
  since v1.0.0 PROPOSED.

TRAIN-008 (3-surface drift cli + registry + test) — PARTIAL_ALGORITHM_LEVEL
  Live verification 2026-05-04: cargo test -p apr-cli --test
  cli_commands registered_commands → "1 passed; 0 failed". The
  test_no_unregistered_commands integration test walks the live clap
  parser and enforces every Subcommand variant matches apr-cli-commands-v1.yaml,
  binding the invariant from feedback_cli_subcommand_three_surface_drift.

TRAIN-009 (end-to-end smoke beats from-scratch baseline) — BLOCKER_FIXTURE_ABSENT
  Honest blocker note: discharge requires the missing real-training
  implementation per §35 (apr distill --stage train is currently a
  stub). Without gradient descent there is no val_loss to compare.
  Path to DISCHARGED documented in the algorithm_evidence notes.

Five Whys
1. Why bind these now? Tasks #218/#247 claimed PARTIAL on 2026-04-30
   but the YAML had no algorithm_evidence. Same drift pattern as
   TRAIN-005/006 (PRs #1438, #1439) — closing it gives the contract a
   complete provability surface.
2. Why mark TRAIN-009 BLOCKER_FIXTURE_ABSENT instead of unbound? It
   has a clear test design (tests/distill_smoke.rs) and a clear
   blocker (real training implementation per §35). Marking it as a
   blocker rather than leaving it untyped makes the dependency
   explicit so a future PR cannot accidentally promote it without
   the real-training prerequisite.
3. Why two PARTIAL + one BLOCKER, not three PARTIAL? PARTIAL implies
   an existing test exercises the invariant. TRAIN-009 has no test
   today (no `tests/distill_smoke.rs`) and cannot have one until §35
   lands. Honest classification beats false PARTIAL claims.
4. Why all three in one PR? They're the last three falsifiers in this
   contract; bundling them produces a single audit story (9/9
   falsifiers now have status). Per Toyota Way each falsifier is a
   distinct binding decision but they share the same review surface.
5. Why bounded? ~45 LOC of YAML, no production code change, no new
   tests (uses existing cargo test + pv validate). pv validate exits
   0 verified locally.

Net effect
- All 9 TRAIN-* falsifiers in apr-cli-distill-train-v1 now have
  algorithm_evidence blocks (8× PARTIAL_ALGORITHM_LEVEL +
  1× BLOCKER_FIXTURE_ABSENT).
- Contract drift between task list (#218/#247) and YAML closed.
- Coverage tally: 15+35 → 15+37 (+2 PARTIAL_ALGORITHM_LEVEL closed,
  TRAIN-009 explicitly blocked not counted).
- MODEL-2 ship %: 56% → 57% (last falsifier-binding gap closed for
  the distill contract; real-training implementation per §35 is the
  only remaining MODEL-2 lever).
- pv validate exits 0.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>