feat(llm): refresh free-tier chain with verified-live OpenRouter IDs

src/llm/explainer.py

@@ -58,18 +58,18 @@ _LLM_TEMPERATURE = 0.3
 # 5xx (upstream), we advance to the next model. Network/timeout errors fall
 # straight to the deterministic template — switching models won't help.
 # Override at runtime via OPENROUTER_FREE_MODELS (comma-separated). Model
-# availability on OpenRouter churns; an ID that 404s is skipped silently.
+# availability on OpenRouter churns; verify with scripts/diagnose_openrouter.py.
 _DEFAULT_FREE_MODEL_CHAIN: tuple[str, ...] = (
-    "inclusionai/ling-2.6-1t:free",                        # ~1T flagship
-    "nvidia/nemotron-3-super-120b-a12b:free",              # 120B reasoning MoE
-    "minimax/minimax-m2.5:free",
-    "tencent/hy3-preview:free",                            # MoE + reasoning
-    "google/gemma-4-31b-it:free",
-    "google/gemma-4-26b-a4b-it:free",
-    "nvidia/nemotron-3-nano-omni-30b-a3b-reasoning:free",
-    "poolside/laguna-m.1:free",
-    "poolside/laguna-xs.2:free",
-    "meta-llama/llama-3.2-3b-instruct:free",               # 3B last-resort
+    "inclusionai/ling-2.6-1t:free",                        # ~1T flagship — verified OK, returns content
+    "nvidia/nemotron-3-super-120b-a12b:free",              # 120B — verified OK, returns content
+    "minimax/minimax-m2.5:free",                           # MoE — verified OK, returns content
+    "google/gemma-4-31b-it:free",                          # 31B — currently 429 but valid id
+    "google/gemma-4-26b-a4b-it:free",                      # 26B MoE — currently 429 but valid id
+    "qwen/qwen3-next-80b-a3b-instruct:free",               # 80B — currently 429 but valid id
+    "tencent/hy3-preview:free",                            # MoE preview — verified OK
+    "nvidia/nemotron-3-nano-omni-30b-a3b-reasoning:free",  # 30B reasoning — verified OK
+    "nvidia/nemotron-3-nano-30b-a3b:free",                 # 30B — verified OK
+    "poolside/laguna-xs.2:free",                           # smallest — verified OK
 )