Phase 5 Batch 4: analyzer 规则引擎 + 3 个高层 Tool

- internal/analyzer: 纯函数规则引擎
  - Finding / Severity / Thresholds / Input / StageMetric / ExecutorMetric
  - 3 规则: data_skew (max/min ratio), gc_pressure (GC/CPU ratio),
    bottleneck (shuffle read+write GB)
  - 严重度阶梯: warning / critical (阈值 ×2)
  - Analyze 入口数据驱动 for ... range
  - 11 个单测 (3 规则 × normal/warning/critical + 零除防御)
- fetch_spark_metrics: SHS 业务封装, format=summary 触发 analyzer
- fetch_cluster_env: RM /cluster/info + /cluster/metrics 聚合
- analyze_spark_log: RM 日志降级链 + LLM-Ready Prompt 拼装
  - prompt 结构: cluster 元信息 + log source + log tail +
    heuristic findings + suggested LLM analysis
  - findings 是 first-pass filter, LLM 做最终判断
- deps.go: +AnalyzerThresholds
- main.go: 注入 cfg 的 3 个阈值
- 端到端实测: analyze_spark_log 完整 prompt 渲染

完成 11 个 Tool 表面 (list_clusters / spark_submit / 4 RM /
fetch_spark_metrics / fetch_cluster_env / analyze_spark_log /
fetch_url / upload_file)

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

internal/analyzer/types.go

@@ -0,0 +1,47 @@
+package analyzer
+
+// Severity is the heuristic finding severity.
+type Severity string
+
+const (
+	SeverityInfo     Severity = "info"
+	SeverityWarning  Severity = "warning"
+	SeverityCritical Severity = "critical"
+)
+
+// Finding is a single triggered heuristic rule.
+type Finding struct {
+	Rule     string         `json:"rule"`
+	Severity Severity       `json:"severity"`
+	Stage    string         `json:"stage,omitempty"`
+	Evidence map[string]any `json:"evidence"`
+	Message  string         `json:"message"`
+}
+
+// Thresholds holds analyzer thresholds injected at runtime.
+type Thresholds struct {
+	DataSkewRatio       float64
+	GCPressureRatio     float64
+	BottleneckShuffleGB float64
+}
+
+// Input is the data passed to the heuristic rules.
+type Input struct {
+	StageMetrics    map[string]StageMetric    `json:"stage_metrics"`
+	ExecutorMetrics map[string]ExecutorMetric `json:"executor_metrics"`
+}
+
+// StageMetric contains per-stage measurements.
+type StageMetric struct {
+	DurationMS        int64 `json:"duration_ms"`
+	ShuffleReadBytes  int64 `json:"shuffle_read_bytes"`
+	ShuffleWriteBytes int64 `json:"shuffle_write_bytes"`
+	MaxPartitionBytes int64 `json:"max_partition_bytes"`
+	MinPartitionBytes int64 `json:"min_partition_bytes"`
+}
+
+// ExecutorMetric contains per-executor measurements.
+type ExecutorMetric struct {
+	GCTimeMS  int64 `json:"gc_time_ms"`
+	CPUTimeMS int64 `json:"cpu_time_ms"`
+}