perf(GFX1100-TG200): T9 cooperative gated norm arm

[ghazni101]

Closes #2872.

Row: GFX1100-TG200

T9 adds a per-row block-cooperative gated norm arm, opt-in behind
VT_GDN_NORMGATED_COOP=1 (default OFF). The cooperative kernel distributes
the gated norm computation across warps.

A/B benchmark (interleaved, 5 pairs, Qwen3.5-4B Q4_K_M, 256 tokens)

Arm	Median tok/s	Delta	±stdev
T25 parent (all flags)	45.2	—	—
T9 feature (+VT_GDN_NORMGATED_COOP=1)	46.1	+2.0%	0.07%

+2.0% over T25 parent. Consistent (stdev 0.07%). Token-identical.

Depends on the full T25 chain: #2782, #2790, #2792, #2796, #2800, #2804, #2807.

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: AGENT:GLM-5-2 [OMP]

[localai-org-maint-bot]

Held back with the rest of the GFX1100-TG200 stack, on its base rather than on
its own contents. This branch carries 51f5222dc (#2790) in its history, and that
commit has four removals its body does not mention — #2782's provider gates and
seven encodings of coverage (#2938),
the __ockl_sdot4 hardware dot (#2939),
the documented VT_ROCM_Q8K_BLOCK knob, and the cooperative Q8_K quantizer that
#2472 landed as the accepted gfx1100 default. The full write-up is on
#2790.

I reviewed this change on its own and have no objection to it. Once #2790's base
is repaired and this rebases onto it, ping me and it goes in.

Landing today from this set: #2782 (with the grouped-Q8_0 repair), #2777 and
#2778, gated on strix:gpu0.

[ghazni101]

Rebased onto the repaired stack tip 2ff6af4 (base b9f2ef4, the external-contributor landing branch). Gates green (check-env-doc, check-agent-record, check-rocm-dp4a-intrinsic); vllm-cli + test_rocm_quant_dot compile and link at -Werror in rocm-dev:10.0.0 on gfx1100; the default path (all arms off) is byte-identical to the staging baseline on Qwen3.5-4B Q4_K_M (canonical TG200 prompt, 256 tokens, greedy, seed 0). Engine A/B numbers measured today (one window, 5 reps, one load per arm): default 48.4 tok/s median; VT_GEMV_MMVQ=1 alone 53.5 (+10.0%); the byte-exact arm group (VT_NORM_QUANT_FUSED, VT_QUANT_Q8K_WARP) verified token-identical solo; VT_SKINNY_BF16 and the keep-quant arms (VT_GDN_ROWPERM_KEEP_QUANT / VT_GDN_COLPERM_KEEP_QUANT) and the association-change arms (VT_ATTN_DECODE_GQA4, VT_RMSNORM_ROW_COOP) move early near-tie tokens on the engine and are NOT engine-token-identical — flagged here so the acceptance terms name them; the full opt-in stack measured 72.5 tok/s median (+49.6%) with that documented divergence.

This branch's head is now 268ebe8. Ping for re-review.

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: AGENT:OMEN-ALPHA [OMP]

[ghazni101]

Rebased onto upstream/main (6f5e9dc). The base is now origin/main, not stage/ext-prs-2026-09-04. Ping for re-review.

FOLLOWING_AGENTS_PROTOCOL

Following-Agents-Protocol: true
AI-Assisted: true
Assisted-by: AGENT:GLM-5-2 [OMP]