feat: Zed edit-predictions keyless FIM route (Qwen2.5-Coder-1.5B / coder-fast)

Deep-research-picked Qwen2.5-Coder-1.5B (BASE, Apache-2.0, native FIM) as a
low-latency inline-completion seat:
- stacks/vllm: vllm-coder service (ana-ml2 GPU1 :8020) + granite shrunk
  (util 0.27->0.13, max-len 131072->16384, seqs 1024->256; granite phasing out)
  to free GPU1 room.
- stacks/litellm: coder-fast alias -> :8020 (mode: completion, /v1/completions).
- stacks/zed-fim-proxy (NEW): keyless /v1/completions front door on ana-docker
  :4141 for Zed (which can't send an auth header) — POST + path + model
  allowlist, injects a coder-fast-scoped virtual key -> LiteLLM :4000. Anon
  /ping liveness. Verified keyless FIM end-to-end.

Zed api_url = http://10.250.50.70:4141/v1, model coder-fast, prompt_format qwen.
Source-IP allowlist off pending the Mac's observed source IP.

stacks/litellm/conf/config.yaml

@@ -257,6 +257,24 @@ model_list:
     model_info:
       mode: rerank
 
+  # --- coder-fast → Qwen2.5-Coder-1.5B (BASE), FIM code-completion seat (ana-ml2
+  #     GPU1 :8020, vLLM; deep-research pick 2026-07-27). For Zed editor inline
+  #     edit-predictions via the LEGACY /v1/completions endpoint with Qwen FIM
+  #     markers (<|fim_prefix|>/<|fim_suffix|>/<|fim_middle|>). BASE not -Instruct
+  #     (FIM is a pretraining objective; base completions are cleaner). Apache-2.0.
+  #     mode: completion — this is text-completion, not chat. Reached KEYLESS from
+  #     Vuong's Mac via the zed-fim-proxy (separate port on ana-docker) which injects
+  #     a coder-fast-scoped virtual key; the proxy's model-allowlist + the scoped key
+  #     bound the blast radius. Runner-up was Qwen2.5-Coder-3B (higher HumanEval-FIM,
+  #     non-commercial Qwen-Research license). ---
+  - model_name: coder-fast
+    litellm_params:
+      model: hosted_vllm/qwen2.5-coder-1.5b
+      api_base: http://10.250.50.54:8020/v1
+      api_key: os.environ/VLLM_API_KEY
+    model_info:
+      mode: completion
+
   # --- z.ai GLM (cloud API) — fronted for unified logging across local
   #     + cloud inference. Explicit entries, so they win over the "*"
   #     wildcard below (no collision with llama-swap's glm4.7-flash etc.