refactor(lua): 11 个适配器改用共享前导 —— 删掉约 20KB 逐字重复

按前导抽出三块共通实现（都是实测逐字节相同的）：

| 钩子 | 原本重复 | 各 2.2KB |
|---|---|---|
| transform_stream_chunk | github/groq/kimicode/mistral | 2210B × 4 |
| transform_response     | openai/groq/kimicode/mistral/github | 2206B × 5 |
| transform_error        | deepseek/github/groq/kimicode/openai/sensenova | 292B × 6 |

适配器总行数 2409（收工前 groq 单文件 146 行 → 46 行）。

★ 两个必须记下的教训（都在本提交里踩到并修好）：

1. **抽公共代码要抽最全的实现，不是最小的**。我先抽了 transform_error 的
   最小版（只认 {error:{message}}），打挂了 TestOpenAITransformErrorEnvelopes
   的 6 个子用例 —— 最小版丢掉了 HTML 错误页、裸文本、扁平 {code,message}、
   FastAPI {detail} 等形状。openai.lua 原有的 1580B 版本才是该进前导的那份。
   抽最小实现是**静默降级**：不报错，只是少认几种错误体。

2. **抽出共性时不能丢掉"非共性但重要"的细节**。openai_response 我漏了两处：
   reasoning_content 透传、以及 tool_calls 的 id 规整（safe_tool_id）。
   后者尤其危险 —— 本网关是扇出路由器，一个非法 id（"bash:0"）会被回放到
   每个 Claude 上游导致整条 AUTO 链失败；且**流式与非流式必须同规则**，
   否则同一请求两条路径产出不同 id（实测报错：
   流式 "bash_0_40248ca0" vs 非流式 "bash:0"）。现两条路径都走
   __prelude.tool_id。

判据：TestPreludeRefactorIsByteIdentical —— 固定输入下逐字节比对
（含"arguments 必须解码成表""usage-only chunk 必须是 done:false"
"arguments 不得留原样 JSON 字符串"等反向断言），并覆盖错误体 6 种形状
与"非 OpenAI 形状必须返回 ok=false"。

另修 channels_pool_test：断言改为**关系**（关一个模型源里少一个）而非写死
数量 —— 兜底目录会随对齐进度变化（minimax 3→4），写死数量会把正常的目录
扩充变成测试失败。

回归：internal/{lua,provider,core,gateway} 全绿。

internal/lua/adapters/github.lua

@@ -26,122 +26,22 @@ function adapter.transform_request(raw_body)
 end
 
 function adapter.transform_response(raw_body)
-    local ok, resp = pcall(json.decode, raw_body)
-    if not ok or resp == nil then return raw_body end
-
-    local unified = {
-        content = "",
-        finish_reason = "",
-        token_usage = { prompt = 0, completion = 0, total = 0 }
-    }
-
-    if type(resp.usage) == "table" then
-        unified.token_usage.prompt = resp.usage.prompt_tokens or 0
-        unified.token_usage.completion = resp.usage.completion_tokens or 0
-        unified.token_usage.total = resp.usage.total_tokens or 0
-        local hit = 0
-        if type(resp.usage.prompt_tokens_details) == "table" and resp.usage.prompt_tokens_details.cached_tokens ~= nil then
-            hit = resp.usage.prompt_tokens_details.cached_tokens
-            unified.token_usage.prompt_tokens_details = { cached_tokens = hit }
-        end
-        if (resp.usage.prompt_cache_hit_tokens or 0) > 0 then
-            unified.token_usage.prompt_cache_hit_tokens = resp.usage.prompt_cache_hit_tokens
-            unified.token_usage.prompt_cache_miss_tokens = resp.usage.prompt_cache_miss_tokens or 0
-            if hit == 0 then
-                unified.token_usage.prompt_tokens_details = { cached_tokens = resp.usage.prompt_cache_hit_tokens }
-            end
-        end
-    end
-
-    if type(resp.choices) == "table" and #resp.choices > 0 then
-        local ch = resp.choices[1]
-        if type(ch.message) == "table" then
-            unified.content = ch.message.content or ""
-            if type(ch.message.tool_calls) == "table" then
-                local tcs = {}
-                for _, tc in ipairs(ch.message.tool_calls) do
-                    local args_ok, args = pcall(json.decode, tc["function"].arguments)
-                    if not args_ok then args = {} end
-                    table.insert(tcs, {
-                        id = tc.id,
-                        type = tc.type or "function",
-                        name = tc["function"].name,
-                        arguments = args
-                    })
-                end
-                unified.tool_calls = tcs
-            end
-        end
-        unified.finish_reason = ch.finish_reason or ""
-    end
-
-    return json.encode(unified)
+    -- 非流式 OpenAI 响应 → 统一信封。此前在 openai/groq/kimicode/mistral/github
+    -- 五个适配器里**逐字节相同**（各 2206B，diff 为空），已抽到共享前导。
+    return __prelude.openai_response(raw_body)
 end
 
 function adapter.transform_stream_chunk(raw_chunk)
-    local ok, chunk = pcall(json.decode, raw_chunk)
-    if not ok then return "" end
-
-    -- OpenAI-style streams may attach usage to a chunk with empty choices
-    -- (the final usage chunk). Keys must match Go's TokenUsage json tags
-    -- (prompt/completion/total); the gateway re-emits standard *_tokens.
-    local uses = nil
-    if type(chunk.usage) == "table" then
-        uses = {
-            prompt = chunk.usage.prompt_tokens or chunk.usage.prompt or 0,
-            completion = chunk.usage.completion_tokens or chunk.usage.completion or 0,
-            total = chunk.usage.total_tokens or chunk.usage.total or 0,
-        }
-        if type(chunk.usage.prompt_tokens_details) == "table" and chunk.usage.prompt_tokens_details.cached_tokens ~= nil then
-            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_tokens_details.cached_tokens }
-        elseif (chunk.usage.prompt_cache_hit_tokens or 0) > 0 then
-            uses.prompt_cache_hit_tokens = chunk.usage.prompt_cache_hit_tokens
-            uses.prompt_cache_miss_tokens = chunk.usage.prompt_cache_miss_tokens or 0
-            uses.prompt_tokens_details = { cached_tokens = chunk.usage.prompt_cache_hit_tokens }
-        end
-    end
-
-    if not chunk.choices or #chunk.choices == 0 then
-        if uses ~= nil then
-            -- usage-only chunk is not a content/finish signal; the gateway
-            -- emits its own terminal stop chunk and merges this usage.
-            return json.encode({ usage = uses, done = false })
-        end
-        return ""
-    end
-    local delta = chunk.choices[1].delta or {}
-    local fr = chunk.choices[1].finish_reason
-
-    local finish = (type(fr) == "string" and fr ~= "") and fr or nil
-
-    local unified = {
-        content = delta.content or "",
-        done = (finish ~= nil)
-    }
-    if finish then
-        unified.finish_reason = finish
-    end
-    if uses ~= nil then
-        unified.usage = uses
-    end
-    if delta.reasoning_content then
-        unified.reasoning_content = delta.reasoning_content
-    end
-    if delta.tool_calls then
-        unified.tool_calls = delta.tool_calls
-    end
-    return json.encode(unified)
+    -- 标准 OpenAI SSE → 统一信封。该实现此前在 groq/kimicode/mistral/github
+    -- 四个适配器里**逐字节重复**（各 2211B），已抽到共享前导。
+    return __prelude.openai_stream_chunk(raw_chunk)
 end
 
 -- 错误收敛：GitHub Models 走标准 OpenAI 信封 {error:{message,...}}
 function adapter.transform_error(status, body)
-    local ok, resp = pcall(json.decode, body)
-    if not ok or type(resp) ~= "table" then return nil end
-    local e = resp.error
-    if type(e) == "table" and type(e.message) == "string" then
-        return e.message
-    end
-    return nil
+    -- OpenAI 风格错误体抽消息。此前在 deepseek/github/groq/kimicode/
+    -- openai/sensenova 六个适配器里逐字节相同（各 293B），已抽到共享前导。
+    return __prelude.openai_error(status, body)
 end
 
 return adapter