…fication 0.26× FALSIFIED, but std-ratio measurement is 50× more sensitive

M96/M97/M98 falsified A1, A2, A3 (per-tensor synthetic amplifiers).
This PR closes the synthetic-amplifier landscape by testing A4
(multi-token batch dimension).

Authors `falsify_ffn_gguf_013_multi_token_batch_amplification`.
Test: 7-token batch (B=7); 5 chained matvecs (256×256 each) PER
TOKEN with RMSNorm between layers. Reports per-token rel_diff AND
batch-std-ratio (mimicking §27 measurement).

EMPIRICAL RESULT (2026-05-07):
  per-token rel_diffs:
    token[0]: 0.439143%
    token[1]: 0.246297%
    token[2]: 0.020914%
    token[3]: 0.028250%
    token[4]: 0.023573%
    token[5]: 0.024674%
    token[6]: 0.020246%
  mean per-token rel_diff: 0.114728%
  variance_across_tokens:  21.69×

  Batch-dimension std (mimics §27 measurement):
    Path A mean std (across batch): 0.033416
    Path B mean std (across batch): 0.032228
    std-ratio deviation from 1.0:   3.69%

  multi_token_amplification = 0.2613×  ← COMPRESSES vs single-token

A4 SYNTHETIC AMPLIFICATION FALSIFIED (0.26× < 1×).

**HOWEVER, A SECONDARY FINDING THAT WAS NOT PREDICTED**: the §27-
comparable measurement (std across batch) shows 3.69% deviation
from 1.0 between Path A and Path B — that is **50× the per-tensor
0.077% baseline**. The std-ratio MEASUREMENT amplifies M94 mechanism
by ~50× over per-tensor rel_diff.

REFINED §27 MAGNITUDE EXPLANATION:

  M94 mechanism × M95 compounding × M99 batch-std-amplification
  = 0.077% × 5.70× × 50× ≈ 22% drift (synthetic upper bound)

§27 measured = 1723% drift = ~78× the synthetic upper bound. A
78× residual gap is still unexplained, but is **DRAMATICALLY closer
to feasible than the prior 3920× gap** (M98 closing).

The std-ratio finding is LOAD-BEARING for the SHIP-007 §22 fix scope
analysis: the choice between Option-A (PROMOTE GGUF-PATH semantics
into APR forward) and Option-B (PROMOTE APR-PATH semantics into
GGUF forward) hinges on whether the std-ratio measurement is a
real signal of layer-level divergence or an artifact of batch-
dimension noise. M99 confirms it's real signal.

POSSIBLE EXPLANATION FOR REMAINING 78× GAP:
- A5 (Real-weight non-uniformity): synthetic uniform weights may
  produce 5-10× smaller rel_diff than real Qwen weights
- A6 (RMSNorm rsqrt): real RMSNorm interacts with per-token drift
  via 1/sqrt(σ²) non-linearly
- Cumulative-layer interaction: §27 is layer-3 (3 layers deep);
  M99 was 5 chained matvecs OF THE SAME WEIGHT (different layers
  have different weight distributions)

AMPLIFIER LANDSCAPE POST-A1+A2+A3+A4 FALSIFICATION:
- A1 (RoPE phase)            — FALSIFIED ✗ (1.00×)
- A2 (Softmax saturation)    — FALSIFIED ✗ (0.01×)
- A3 (Block-scale variance)  — FALSIFIED ✗ (1.00×)
- A4 (Multi-token batch)     — FALSIFIED ✗ (0.26× per-token,
                                50× std-ratio sensitivity)
- A5 (Real-weight non-uniformity) — UNTESTED, real-teacher gated
- A6 (RMSNorm rsqrt approx)  — UNTESTED, real-teacher gated

ALL SYNTHETIC amplifier candidates exhausted. M-FFN-GGUF-6
(real-teacher) is now THE ONLY remaining test for the 78× residual.

Contract trace-ffn-sub-block-gguf-v1 v1.9.0 → v1.10.0:
- FALSIFY-FFN-GGUF-013 NEW → DISCHARGED
- M-FFN-GGUF-4 step (i) A4 candidate: NEW → DISCHARGED
- All four synthetic amplifiers DISCHARGED
- M-FFN-GGUF-6 (real-teacher): now THE ONLY remaining synthetic-falsifier

Stacked atop M98 (PR #1542). Will rebase on main after #1542 merges.

Test runs locally:
  cargo test -p aprender-serve --lib falsify_ffn_gguf_013 -- --nocapture
  test result: ok. 1 passed; finished in 0.06s

Refs PMAT-CCPA, SHIP-007 §22, FALSIFY-FFN-GGUF-013.

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