…-003/004/007 drift (round 2)

Second-round test-reference drift correction. §57's drift sweep
(this contract's v1.4 → v1.5 bump in PR #1505) caught FALSIFY-005/006
but a more thorough audit (cross-referencing every `test:` field
against the source-code function-name registry) surfaced three
additional dangling references.

## Drift inventory (round 2)

  | Falsifier | v1.5.0 cited test                                           | Exists? | Actual test                                                  |
  | ---       | ---                                                         | ---     | ---                                                          |
  | 003       | build_transformer_config_qwen_init_matches_constructor      | ❌       | build_transformer_config_qwen_init_matches_input             |
  | 004       | transformer::attention::tests::gqa_7_to_1_matches_full_mha  | ❌       | transformer::model::tests::falsify_apr_pretrain_arch_004_*   |
  | 007       | build_transformer_config_encoder_init_errors                | ❌       | validate_pretrain_init_arch_rejects_encoder                  |

## Why §57 (PR #1505) didn't catch these

§57's grep audited test-name SUFFIXES and FRAGMENTS, which produced
false-negatives on:
  - `_init_matches_constructor` vs `_init_matches_input` — both end
    in `_matches_<word>` so a fragment grep counted the contract's
    name as "not dangling"
  - `transformer::attention::tests::` vs `transformer::model::tests::` —
    module-path drift not just function-name drift; only fully-
    qualified path comparison catches this
  - `_encoder_init_errors` vs `validate_pretrain_init_arch_rejects_encoder` —
    the contract's name was a guess at the impl name; impl PR #1479
    chose a completely different convention

## How this round was found

Used a stricter audit: for every `cargo test ... ::tests::<name>`
in contracts, grep `fn <name>` in the actual source tree. If the
fn doesn't exist, drift. This catches drift that PR #1505's
fragment-based audit missed.

## Resolution

Update FALSIFY-003/004/007 `test:` fields to the actual function
names. No falsifier semantics change. 11 falsifiers all PASS;
contract status remains FUNCTIONAL.

## Verification

  $ cargo test -p aprender-train --lib -- build_transformer_config_qwen_init_matches_input
    test result: ok. 1 passed
  $ cargo test -p aprender-train --lib -- falsify_apr_pretrain_arch_004_gqa_7_1_forward_pass_smoke
    test result: ok. 1 passed
  $ cargo test -p aprender-train --lib -- validate_pretrain_init_arch_rejects_encoder
    test result: ok. 1 passed
  $ pv validate contracts/apr-pretrain-arch-polymorphic-v1.yaml
    0 error(s), 0 warning(s)

## Five Whys

1. Why did §57's sweep miss these? Used name-fragment grep
   (`::tests::[a-z_]+`) which counted false-negatives on suffix-
   close names like `_constructor` ↔ `_input`.
2. Why is module-path drift a separate class? Because grep against
   the `[a-z_]+` regex captures the FUNCTION name, not the
   `::module::tests::` path. A function with the right name in the
   wrong module passes that audit but fails actual test invocation.
3. Why fix in a separate PR rather than amending PR #1505? PR #1505
   already merged. Per `feedback_falsifier_first_cascade_pattern.md`
   the cleanest cadence is one-bump-per-PR.
4. Why bump to v1.6.0? Same pattern as PR #1505's v1.4 → v1.5: the
   test-binding INVARIANT was broken in v1.5.0 (residual drift) and
   v1.6.0 restores it.
5. Why now (during 5g.1 wait)? Productive use of the 5g.1 (~10hr
   remaining) compute-bound idle time. Each drift fix is small
   (~30 LOC), reduces drift risk for future agents, and restores
   the falsifier-binding invariant. The alternative (manufacture
   bigger work) would risk introducing defects the contract base
   doesn't catch yet.

## Net effects

- Contract v1.5.0 → v1.6.0 FUNCTIONAL.
- 11 falsifiers, all PASS — same count, but FALSIFY-003/004/007
  now reference tests that actually exist.
- MODEL-1 ship % unchanged at 91%.
- MODEL-2 ship % unchanged at 57% until 5g.3.

This is the SECOND round of drift sweep on this contract. Together
with PRs #1502/#1504/#1505/#1506 (round 1), all known
test-reference drift is closed across the §50.4 cascade contracts.
A future spec amendment could codify a `pv lint --strict-test-binding`
enforcement that prevents drift at contract-merge time.

Refs: SPEC-SHIP-TWO-001 §50.4 cascade,
      contracts/apr-pretrain-arch-polymorphic-v1.yaml v1.6.0,
      PR #1505 (round 1 partial fix), PR #1502/#1504/#1506 (sibling fixes)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

…-003-004-007-drift

…nd 2.5 — surfaced by PR #1511)

Round 2 (initial commit on this branch) fixed FALSIFY-003/004/007.
Sub-agent PR #1511 (`pv lint --strict-test-binding`) surfaced a 4th
drift in this same contract:

  FALSIFY-001 cited `qwen2_0_5b_matches_hf_config`
    → does NOT exist on main.
  Actual: `qwen2_0_5b_matches_hf_config_2026_05_04`
    (date-suffix added by impl PR #1474 / commit 9af6e71 — May 4).

The earlier round-2 audit (which focused on suffix + module-path
drift) didn't catch this because the test name has a DATE-SUFFIX
drift class (function name + `_<date>` is a real Rust test, but
the contract truncated to the prefix).

Updates:
- FALSIFY-001 test ref: append `_2026_05_04` suffix.
- v1.6.0 changelog updated to record 4 fixes (was 3).
- Verified: cargo test qwen2_0_5b_matches_hf_config_2026_05_04 PASS.
- pv lint --strict-test-binding contracts/apr-pretrain-arch-polymorphic-v1.yaml: 0 PV-VER-002 (down from 4 pre-fix).

This consolidates round 2 into a single commit on the same branch
+ PR (#1509) rather than spawning a round-3 PR for one extra fix.
The lint hardening in #1511 is what made finding the 4th drift
trivial; future drift will be caught at contract-merge time once
#1511 lands.

Refs: SPEC-SHIP-TWO-001 §50.4 cascade,
      PR #1511 (sub-agent's pv lint --strict-test-binding),
      Issue #1510

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>