…yaml (closes #1858)

The QA-002 falsifier (`enforcement.kernel_registry_complete`) detected
five fused kernels that exist in the codebase but lack `fusion_decisions`
entries. Now registered as FUSION-006..010, all status ACTIVE with
verified call sites.

## Why this matters

Without entries, these kernels are invisible to:
- `pv lint` / contract-coverage audits
- The BLOCKED-requires-benchmark rule (QA-003)
- The Poka-Yoke registry check (kernel_registry_complete)

The drift was previously masked because the falsifier tests couldn't
compile (broken `include_str!` paths repaired in #1857 / #1860).
Repairing those paths surfaced the drift in `fusion_gate_contract_falsify`
(aprender-serve) and `falsify_fusion_001_every_fused_kernel_has_yaml_entry`
(aprender-gpu).

## Five entries added

| ID         | Kernel                            | Replaces                          | Call site |
|------------|-----------------------------------|-----------------------------------|-----------|
| FUSION-006 | FusedQKVKernel                    | Q/K/V GEMVs                       | crates/aprender-serve/src/cuda/generate.rs:267 |
| FUSION-007 | FusedGateUpKernel                 | Gate+Up GEMV + SwiGLU (FP32 path) | crates/aprender-serve/src/cuda/generate.rs:270 |
| FUSION-008 | FusedGemmBiasGeluKernel           | GEMM + Bias + GELU                | crates/aprender-gpu/src/memory/resident/ops/composite/linear_bias.rs:232 |
| FUSION-009 | FusedRmsNormQ4KGemvKernel         | RMSNorm + Q4K GEMV                | crates/aprender-serve/src/cuda/generate.rs:202 |
| FUSION-010 | FusedGateUpQ4KGemvKernel          | Gate+Up Q4K GEMVs (shared input)  | crates/aprender-serve/src/cuda/generate.rs:273 |

Each kernel was confirmed via `grep -rn 'pub struct <Name>\b'` and
each call site verified by inspecting the dispatching file.

FUSION-007 vs FUSION-010 distinction documented inline:
- FUSION-007 = FP32-input gate+up+SwiGLU fused (FusedGateUpKernel)
- FUSION-010 = Q4K-input gate+up sharing input vector load
  (FusedGateUpQ4KGemvKernel); SwiGLU applied separately downstream.

## Verification

```
$ cargo run -p aprender-contracts-cli --bin pv -- validate \
    contracts/kernel-fusion-v1.yaml
Contract is valid.

$ cargo test -p aprender-serve --test fusion_gate_contract_falsify --release
test result: ok. 5 passed; 0 failed     ← was 4/5 with QA-002 failing

$ cargo test -p aprender-gpu --features cuda --lib --release \
    falsify_fusion_001_every_fused_kernel_has_yaml_entry
test result: ok. 1 passed; 0 failed     ← was failing on FusedQKVKernel
```

Closes #1858.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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