chore: expand OpenRouter list per feedback — Claude 4.5 gen, Opus, R1, Maverick, Mistral

OpenRouter / _FALLBACK_MODELS (7 → 13 models):
- Add gpt-5.4 (full OpenAI alongside Mini)
- Restore claude-sonnet-4-5 (keep 4.5 generation alongside 4.6)
- Add claude-opus-4.6 (flagship)
- Add deepseek-r1 (popular reasoning model)
- Add llama-4-maverick (larger open-weight option)
- Add mistral-large-latest (Mistral via OpenRouter)

Structural:
- Add mistralai to _PROVIDER_MODELS for correct prefix-stripping routing
- Add mistralai to _PROVIDER_DISPLAY for correct group label

api/config.py

@@ -406,13 +406,25 @@ CLI_TOOLSETS = get_config().get("platform_toolsets", {}).get("cli", _DEFAULT_TOO
 # Hardcoded fallback models (used when no config.yaml or agent is available)
 # Also used as the OpenRouter model list — keep this curated to current, widely-used models.
 _FALLBACK_MODELS = [
+    # OpenAI
     {"provider": "OpenAI",    "id": "openai/gpt-5.4-mini",                "label": "GPT-5.4 Mini"},
+    {"provider": "OpenAI",    "id": "openai/gpt-5.4",                     "label": "GPT-5.4"},
+    # Anthropic — 4.6 flagship + 4.5 generation
+    {"provider": "Anthropic", "id": "anthropic/claude-opus-4.6",          "label": "Claude Opus 4.6"},
     {"provider": "Anthropic", "id": "anthropic/claude-sonnet-4.6",        "label": "Claude Sonnet 4.6"},
+    {"provider": "Anthropic", "id": "anthropic/claude-sonnet-4-5",        "label": "Claude Sonnet 4.5"},
     {"provider": "Anthropic", "id": "anthropic/claude-haiku-4-5",         "label": "Claude Haiku 4.5"},
+    # Google
     {"provider": "Google",    "id": "google/gemini-3.1-pro",              "label": "Gemini 3.1 Pro"},
     {"provider": "Google",    "id": "google/gemini-3-flash",              "label": "Gemini 3 Flash"},
-    {"provider": "DeepSeek",  "id": "deepseek/deepseek-chat-v3-0324","label": "DeepSeek V3"},
+    # DeepSeek
+    {"provider": "DeepSeek",  "id": "deepseek/deepseek-chat-v3-0324",     "label": "DeepSeek V3"},
+    {"provider": "DeepSeek",  "id": "deepseek/deepseek-r1",               "label": "DeepSeek R1"},
+    # Meta
     {"provider": "Meta",      "id": "meta-llama/llama-4-scout",           "label": "Llama 4 Scout"},
+    {"provider": "Meta",      "id": "meta-llama/llama-4-maverick",        "label": "Llama 4 Maverick"},
+    # Mistral
+    {"provider": "Mistral",   "id": "mistralai/mistral-large-latest",     "label": "Mistral Large"},
 ]
 
 # Provider display names for known Hermes provider IDs
@@ -435,6 +447,7 @@ _PROVIDER_DISPLAY = {
     "opencode-zen": "OpenCode Zen",
     "opencode-go": "OpenCode Go",
     "lmstudio": "LM Studio",
+    "mistralai": "Mistral",
 }
 
 # Well-known models per provider (used to populate dropdown for direct API providers)
@@ -552,6 +565,11 @@ _PROVIDER_MODELS = {
         {"id": "gemini-3.1-pro", "label": "Gemini 3.1 Pro"},
         {"id": "gemini-3-flash", "label": "Gemini 3 Flash"},
     ],
+    # Mistral — prefix used in OpenRouter model IDs (mistralai/mistral-large-latest)
+    "mistralai": [
+        {"id": "mistral-large-latest", "label": "Mistral Large"},
+        {"id": "mistral-small-latest", "label": "Mistral Small"},
+    ],
 }