feat: ModelRouter — unified OpenAI-compatible multi-source LLM gateway

- Lua adapters per upstream (transform_request/response/stream_chunk, build_headers signing hooks)
- AUTO priority routing with per-model kind (chat/image), explicit source/model routing
- Per-source concurrency caps with queueing, exponential backoff, AUTO failover
- OpenAI-compatible API: chat completions, SSE streaming, image generations, models
- Gateway key auth, web UI for adapter/source management, runtime persistence
- e2e test running the real binary against mocked upstreams

internal/lua/adapters/ollama.lua

@@ -0,0 +1,63 @@
+local adapter = {}
+
+adapter.name = "ollama"
+adapter.version = "2.0.0"
+adapter.endpoint = "/api/chat"
+adapter.headers = {}
+
+-- Ollama API 格式：{ model, messages, stream, options:{temperature,num_predict} }
+function adapter.transform_request(raw_body)
+    local ok, req = pcall(json.decode, raw_body)
+    if not ok then return raw_body end
+
+    local ollama_req = {
+        model = req.model or "llama3",
+        stream = req.stream or false,
+        options = {
+            temperature = req.temperature or 0.7,
+            num_predict = req.max_tokens or 2048
+        }
+    }
+
+    -- 转换 messages 格式（Ollama 兼容 OpenAI 的 messages 格式）
+    if req.messages then
+        local msgs = {}
+        for _, m in ipairs(req.messages) do
+            table.insert(msgs, { role = m.role, content = m.content })
+        end
+        ollama_req.messages = msgs
+    end
+
+    return json.encode(ollama_req)
+end
+
+function adapter.transform_response(raw_body)
+    local ok, resp = pcall(json.decode, raw_body)
+    if not ok then return raw_body end
+
+    local unified = {
+        content = "",
+        finish_reason = resp.done_reason or "",
+        tool_calls = {},
+        usage = { prompt = 0, completion = 0, total = 0 }
+    }
+
+    if resp.message then
+        unified.content = resp.message.content or ""
+    end
+
+    return json.encode(unified)
+end
+
+function adapter.transform_stream_chunk(raw_chunk)
+    local ok, chunk = pcall(json.decode, raw_chunk)
+    if not ok then return "" end
+    if not chunk.message then return "" end
+
+    return json.encode({
+        content = chunk.message.content or "",
+        done = chunk.done or false
+    })
+end
+
+return adapter