feat(routing): 引入多执行池智能调度

将 Worker 发现、路由画像、容量与执行传输抽象为平台无关接口，新增 Kubernetes 和静态容量适配器，并以 shadow 模式接入生产配置。

实现网络与容量评分、路由防抖、池队列、同步 Worker 租约、一次性执行令牌，以及提交状态不明时禁止重复分配的安全语义。

新增 0105 兼容迁移、管理接口、指标、OpenAPI 和回归测试。已执行全量 Go 测试、go vet、OpenAPI、迁移安全、Compose 与 Kustomize 验证。

apps/api/internal/executionpool/selector_test.go

@@ -0,0 +1,86 @@
+package executionpool
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestSelectorRejectsUnreachableAndPrefersNetwork(t *testing.T) {
+	now := time.Now()
+	selector := NewSelector()
+	decision, err := selector.Select(SelectionRequest{Now: now, Candidates: []SelectionCandidate{
+		candidate("slow", RouteHealthy, now, 120*time.Millisecond, 8, 1),
+		candidate("fast", RouteHealthy, now, 20*time.Millisecond, 8, 1),
+		candidate("down", RouteUnreachable, now, time.Millisecond, 32, 0),
+	}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if decision.PoolID != "fast" {
+		t.Fatalf("pool=%s, want fast", decision.PoolID)
+	}
+	if decision.Rejected["down"] != "route_unreachable" {
+		t.Fatalf("down rejection=%q", decision.Rejected["down"])
+	}
+}
+
+func TestSelectorUsesCapacityAsHardGate(t *testing.T) {
+	now := time.Now()
+	selector := NewSelector()
+	decision, err := selector.Select(SelectionRequest{Now: now, Candidates: []SelectionCandidate{
+		candidate("fast-full", RouteHealthy, now, 10*time.Millisecond, 2, 2),
+		candidate("slower-free", RouteHealthy, now, 80*time.Millisecond, 8, 1),
+	}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if decision.PoolID != "slower-free" {
+		t.Fatalf("pool=%s, want slower-free", decision.PoolID)
+	}
+}
+
+func TestSelectorRejectsUnknownAndStale(t *testing.T) {
+	now := time.Now()
+	selector := NewSelector()
+	_, err := selector.Select(SelectionRequest{Now: now, Candidates: []SelectionCandidate{
+		candidate("unknown", RouteUnknown, now, time.Millisecond, 8, 0),
+		candidate("stale", RouteHealthy, now.Add(-time.Minute), time.Millisecond, 8, 0),
+	}})
+	if !errors.Is(err, ErrNoEligiblePool) {
+		t.Fatalf("err=%v, want ErrNoEligiblePool", err)
+	}
+}
+
+func TestSelectorHonorsHysteresis(t *testing.T) {
+	now := time.Now()
+	selector := NewSelector()
+	fast := candidate("fast", RouteHealthy, now, 20*time.Millisecond, 8, 1)
+	fast.BetterWindows = 3
+	current := candidate("current", RouteHealthy, now, 80*time.Millisecond, 8, 1)
+	decision, err := selector.Select(SelectionRequest{
+		Now: now, Candidates: []SelectionCandidate{fast, current},
+		CurrentPoolID: "current", CurrentPoolSince: now.Add(-time.Minute),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if decision.PoolID != "current" {
+		t.Fatalf("pool=%s, want current during dwell", decision.PoolID)
+	}
+}
+
+func candidate(id string, state RouteState, sampled time.Time, latency time.Duration, capacity, active int) SelectionCandidate {
+	return SelectionCandidate{
+		Pool: ExecutionPool{ID: id, State: PoolActive}, CapabilityMatched: true,
+		Health: RouteHealth{
+			PoolID: id, State: state, SuccessRate: 1, ConnectTLSP95: latency,
+			FirstByteP95: latency, UploadBytesPerSecond: 10 * 1024 * 1024,
+			JitterP95: latency / 10, SampledAt: sampled, ExpiresAt: sampled.Add(45 * time.Second),
+		},
+		Capacity: CapacitySnapshot{
+			PoolID: id, WorkerCount: 1, SafeCapacity: capacity, ActiveTasks: active,
+			ResourceHeadroom: 0.8, Stability: 1,
+		},
+	}
+}