Swap frank-default-large to DFlash2 on Vulkan (PR #27342)

Replace the retired CIRU ROCmFPX runtime with upstream llama.cpp PR #27342
DFlash2 on the Vulkan backend:

- Target: unsloth Qwen3.8-27B-UD-Q8_K_XL.gguf (31.4 GB, already on disk)
- Drafter: z-lab Qwen3.8-27B-DFlash2-Q4_K_M.gguf (block size 8, top-k 16)
- Runtime: /home/dank/llama.cpp-dflash2/build-dflash2/bin/llama-server
  (GGML_VULKAN=ON; HIP lacks TOP_K so the stack runs on Vulkan0/RADV)
- spec: --spec-type draft-dflash --spec-draft-n-max 8 (clamps to 7)

Validated 2026-08-21 on scratch port 52626: mean acceptance 5.27,
health + reasoning completion OK.

Archive the retired CIRU .env/.serve script in .AGENTTRASH.
Update deployment.md, index.md, AGENTS.md; add docs/dflash2-large-vulkan.md.

scripts/frank-default-large.service

@@ -1,5 +1,5 @@
 [Unit]
-Description=CIRU llama.cpp Qwen3.8-27B ActiveFPX PromptForge MTP (dankclaw, frank-default-large)
+Description=llama.cpp DFlash2 Qwen3.8-27B UD-Q8_K_XL + Q4_K_M drafter (dankclaw, frank-default-large)
 After=network-online.target
 Wants=network-online.target