feat(v0.1): add mgr session PVC lifecycle for true session state persistence

PR B for #770: mgr/session-pvc.ts + server endpoints + selftest.

- 新模块 src/mgr/session-pvc.ts: createSessionPvc / getSessionPvcSummary / deleteSessionPvc / refreshSessionPvcSummary / runSessionStorageGc / startSessionStorageGcLoop
- Server 增量 4 个 endpoint:
  * POST /api/v1/sessions: 创建 session 同步创建 PVC
  * GET /api/v1/sessions/:id/storage: 查询 PVC 摘要
  * DELETE /api/v1/sessions/:id/storage: 删 PVC + storage_kind=evicted
  * POST /api/v1/sessions/:id/storage/refresh: runner 上报 PVC 摘要
  * POST /api/v1/sessions/storage/gc: 手动触发 GC
- mgr SA RBAC 已在 PR A 增加；manager server 不直连 Kubernetes API（kubectl 由 mgr 容器内执行）
- SessionRecord 增量 storageKind / storagePvcName / storageNamespace / storageSizeBytes / storageFilesCount / storageSha256 / storageUpdatedAt / storagePvcPhase / storageEvictedAt / codexRolloutSubdir
- kubernetes-runner-job 短路：run 引用 evicted session 时直接返回 session-store-evicted，不创建 runner Job
- KubectlHandler 可注入，selftest 覆盖 create / summary / refresh / eviction / gc / REST 路径
- GC loop 默认 5min（AGENTRUN_SESSION_GC_INTERVAL_MS 可调）

runner / backend / HWLAB adapter 在 PR C / PR D 落地。

src/common/types.ts

@@ -198,8 +198,48 @@ export interface SessionRecord extends JsonRecord {
   createdAt: string;
   updatedAt: string;
   expiresAt: string | null;
+  storageKind?: SessionStorageKind;
+  storagePvcName?: string | null;
+  storageNamespace?: string | null;
+  storageSizeBytes?: number | null;
+  storageFilesCount?: number | null;
+  storageSha256?: string | null;
+  storagePvcPhase?: string | null;
+  storageUpdatedAt?: string | null;
+  storageEvictedAt?: string | null;
+  codexRolloutSubdir?: string;
 }
 
+export type SessionStorageKind = "none" | "pvc" | "evicted";
+
+export interface UpsertSessionInput extends JsonRecord {
+  sessionId: string;
+  tenantId: string;
+  projectId: string;
+  backendProfile: BackendProfile;
+  conversationId: string | null;
+  threadId: string | null;
+  metadata: JsonRecord;
+  expiresAt: string | null;
+  codexRolloutSubdir: string;
+}
+
+export interface SessionStoragePatch extends JsonRecord {
+  sessionId: string;
+  storageKind: SessionStorageKind;
+  pvcName?: string | null;
+  storageNamespace?: string | null;
+  pvcPhase?: string | null;
+  storageSizeBytes?: number | null;
+  storageFilesCount?: number | null;
+  storageSha256?: string | null;
+  codexRolloutSubdir?: string;
+}
+
+export interface ListGcExpiredSessionsInput extends JsonRecord {
+  now: number;
+  limit: number;
+}
 export interface SessionReadCursorRecord extends JsonRecord {
   sessionId: string;
   readerId: string;