docs(paged): record W4A16 Wq padding rejection

Record the Phase 5 Wq shared-memory padding experiment, its gates, sub-threshold benchmark gain, and the decision to ship no 0051 patch.

Assisted-by: Codex:gpt-5

docs/superpowers/plans/2026-06-30-w4a16-wq-pad-phase5.md

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+# W4A16 Wq Shared-Memory Padding Phase 5 Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development or superpowers:executing-plans. Keep checkboxes current while executing.
+
+**Goal:** Test whether padding the grouped W4A16 quantized-weight shared-memory row stride improves the post-`0050` kernel.
+
+**Scope:** Fork-first experiment on top of `0050`. Keep it separate and incremental. Ship no patch unless it passes md5/op gates and improves prefill.
+
+## Task 1: Implement Wq Padding
+
+- [x] Add a Wq shared-memory row-stride constant.
+- [x] Pad Wq rows by 4 `uint32_t` slots.
+- [x] Update only Wq copy and Wq byte-indexing; do not change A padding, Wd layout, dequant math, MMA order, metadata, or launch shape.
+
+## Task 2: Gates
+
+- [x] Build `llama-batched-bench`, `llama-completion`, and `test-backend-ops` on DGX.
+- [x] Run canonical default-off paged MoE and dense greedy md5 gates.
+- [x] Run forced W4A16 `bm32` vs `base` md5 gates.
+- [x] Run forced W4A16 `test-backend-ops test -b CUDA0 -o MUL_MAT_ID -j 1`.
+- [x] Run W4A16 default `bm32` A/B against Phase 4 at `npp=512,2048`.
+
+## Task 3: Disposition
+
+- [x] Keep only if it improves W4A16 prefill by at least 1% at either `npp=512` or `npp=2048` without regressing the other by more than 1%.
+- [x] If kept, commit fork-first with `Assisted-by: Codex:gpt-5`, generate patch `0051`, verify mirror tree hash, update docs, and commit LocalAI. Not taken: perf gate did not clear 1%.
+- [x] If rejected, revert the fork experiment and record the result without adding a patch.
+
+Result: rejected, no fork commit and no LocalAI patch `0051`.
+
+Artifacts:
+
+- Build: `~/llama-w4a16-phase5`
+- Logs: `~/bench/w4a16_phase5`
+
+Gates:
+
+- Canonical paged MoE md5: `8cb0ce23777bf55f92f63d0292c756b0`.
+- Canonical dense md5: `5951a5b4d624ce891e22ab5fca9bc439`.
+- Forced W4A16 `bm32` md5: `07db32c2bcb78d17a43ed18bc22705cd`.
+- Forced W4A16 `base` md5: `07db32c2bcb78d17a43ed18bc22705cd`.
+- Forced W4A16 `MUL_MAT_ID`: `806/806` on CUDA0.
+
+Performance:
+
+| Shape | 512 S_PP t/s | 2048 S_PP t/s | Decision |
+|-------|--------------|---------------|----------|
+| Phase 4 A-pad `bm32` | 1466.62 | 1495.93 | baseline |
+| Phase 5 Wq-pad `bm32` | 1472.36 | 1504.82 | rejected: below 1% gate |
+| Phase 4 A-pad `base` | 1337.88 | 1364.98 | baseline |
+| Phase 5 Wq-pad `base` | 1337.70 | 1368.48 | diagnostic |
+
+Disposition:
+
+- Reverted local fork experiment in `/home/mudler/_git/llama.cpp`.
+- Do not ship Wq padding alone; the measured gain is below the maintenance threshold.