tools: 为 spark_submit 的未 mint 绝对路径增加可观测警告

LLM 有时会把自己本地的绝对路径直接传给 spark_submit；这个路径在 MCP
服务器上不存在，spark-submit 会失败，但当前 translateArgs 是静默透传，
问题难以定位。添加 logger.Warn("spark_submit.unminted_path")，对
服务器未 mint 的绝对路径/路径型参数发出警告，同时保持透传不变。

生产环境中这条警告是诚实的可观测信号，而不是回归指标：集群本地合法路径
（如 /opt/spark/examples/pi.py）也会触发警告，这是设计上的，因为我们
无法区分“合法集群路径”和“LLM 本地路径”。

测试锁定：
- minted_path_no_warn：上传文件返回的 path 不触发警告
- cluster_local_path_warns：未 mint 的绝对路径触发一次警告且 path 正确
- non_path_args_never_warn：--class、Main、--master 等普通参数不触发警告

translateArgs 对 logger 做 nil-safe 处理：测试中 deps.Logger 未设置时不
会 panic，也不会产生日志，保持现有测试的简洁。

Co-Authored-By: Claude <noreply@anthropic.com>

internal/mcp/tools/spark_submit_path_test.go

@@ -1,7 +1,10 @@
 package tools
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
+	"log/slog"
 	"os"
 	"path/filepath"
 	"strings"
@@ -70,6 +73,97 @@ func TestSparkSubmit_PathPassthrough(t *testing.T) {
 	}
 }
 
+func TestTranslateArgs_Logging(t *testing.T) {
+	deps, _ := testDepsWithDataDir(t)
+
+	t.Run("minted_path_no_warn", func(t *testing.T) {
+		store := deps.UploadStore
+		fileID, _, _, _, absPath, err := store.Save([]byte("print('hi')\n"), "hello.py")
+		if err != nil {
+			t.Fatalf("save upload: %v", err)
+		}
+
+		logger, buf := capturingLogger(t)
+		out := translateArgs([]string{absPath, "--class", "Main"}, deps.UploadStore, logger)
+		if out[0] != absPath {
+			t.Errorf("out[0]=%q, want %q", out[0], absPath)
+		}
+
+		for _, rec := range parseLogRecords(t, buf) {
+			if rec["msg"] == "spark_submit.unminted_path" {
+				t.Errorf("unexpected warn for minted path: %v", rec)
+			}
+		}
+
+		if !strings.HasSuffix(absPath, "/"+fileID) {
+			t.Errorf("absPath=%q does not end with fileID %q", absPath, fileID)
+		}
+	})
+
+	t.Run("cluster_local_path_warns", func(t *testing.T) {
+		logger, buf := capturingLogger(t)
+		out := translateArgs([]string{"/opt/spark/examples/pi.py"}, deps.UploadStore, logger)
+		if len(out) != 1 || out[0] != "/opt/spark/examples/pi.py" {
+			t.Errorf("out=%v, want [/opt/spark/examples/pi.py]", out)
+		}
+
+		var warns int
+		for _, rec := range parseLogRecords(t, buf) {
+			if rec["msg"] == "spark_submit.unminted_path" {
+				warns++
+				if rec["path"] != "/opt/spark/examples/pi.py" {
+					t.Errorf("warn path=%v, want /opt/spark/examples/pi.py", rec["path"])
+				}
+			}
+		}
+		if warns != 1 {
+			t.Errorf("warns=%d, want 1; log=%s", warns, buf.String())
+		}
+	})
+
+	t.Run("non_path_args_never_warn", func(t *testing.T) {
+		logger, buf := capturingLogger(t)
+		out := translateArgs([]string{"--class", "Main", "--master", "yarn"}, deps.UploadStore, logger)
+		want := []string{"--class", "Main", "--master", "yarn"}
+		if len(out) != len(want) {
+			t.Fatalf("out=%v, want %v", out, want)
+		}
+		for i := range out {
+			if out[i] != want[i] {
+				t.Errorf("out[%d]=%q, want %q", i, out[i], want[i])
+			}
+		}
+
+		for _, rec := range parseLogRecords(t, buf) {
+			if rec["msg"] == "spark_submit.unminted_path" {
+				t.Errorf("unexpected warn for non-path args: %v", rec)
+			}
+		}
+	})
+}
+
+func capturingLogger(t *testing.T) (*slog.Logger, *bytes.Buffer) {
+	t.Helper()
+	buf := &bytes.Buffer{}
+	return slog.New(slog.NewJSONHandler(buf, &slog.HandlerOptions{Level: slog.LevelDebug})), buf
+}
+
+func parseLogRecords(t *testing.T, buf *bytes.Buffer) []map[string]any {
+	t.Helper()
+	var recs []map[string]any
+	for _, line := range strings.Split(strings.TrimSpace(buf.String()), "\n") {
+		if line == "" {
+			continue
+		}
+		var rec map[string]any
+		if err := json.Unmarshal([]byte(line), &rec); err != nil {
+			t.Fatalf("invalid log JSON: %q (err=%v)", line, err)
+		}
+		recs = append(recs, rec)
+	}
+	return recs
+}
+
 func TestSparkSubmit_ClusterLocalPathPassthrough(t *testing.T) {
 	deps, repo := testDepsWithDataDir(t)
 	deps.SparkSubmitTimeout = 5 * time.Second