feat(worker): 实现集群限流与自适应负载

保留平台模型 RPM、TPM 和并发策略语义，增加 PostgreSQL 集群级租约、饱和候选重选和多平台自动负载，避免突发任务固定等待首个平台。\n\n新增 Worker 实时负载采样、自适应 active/heavy 容量、心跳与管理端指标，并扩展本地 acceptance runner，覆盖三 Worker、同模型三平台 2/4/6 并发和 48 个带图视频突发任务。\n\n验证：go test ./...、go vet ./...、PostgreSQL 跨 Store 集成测试、gofmt、bash -n、ShellCheck 及本地集群 provider-burst 验收通过；48/48 成功，无越限、重复提交、重复计费、重复回调或终态资源泄漏。

scripts/acceptance/report.mjs

@@ -154,7 +154,7 @@ async function loadReports(directory) {
   const reports = [];
   for (const name of entries) {
     const report = await regularJSON(resolve(directory, name));
-    if (report.schemaVersion === 'acceptance-load-report/v1') {
+    if (report.schemaVersion === 'acceptance-load-report/v1' || report.schemaVersion === 'acceptance-load-report/v2') {
       if (report.secretSafe !== true) throw new Error(`load report ${name} is not secret-safe`);
       reports.push({
         file: name,
@@ -163,6 +163,8 @@ async function loadReports(directory) {
         phases: report.phases,
         failure: report.failure,
         failureOperation: report.failureOperation,
+        capacity: report.capacity,
+        cluster: report.cluster,
         startedAt: report.startedAt,
         finishedAt: report.finishedAt
       });