feat(overlay): 内容块级寻址 + 实例逐步拉起 + 骨干选路 + 组密钥加密（序24–㉛ 累积同步）

代码
- 内容分发块级寻址：新增 src/net/relay/content/{chunker,store,runtime,source,peer,crypto}.ts
- 组密钥（C 档）确定性加密：AES-256-GCM，块 id β′ = sha256(密文) 前 32 hex；双 epoch 过渡窗口
- 实例生命周期：三处 teardown() 不再杀实例（local/remote/leased-spawner）；启动认领 + TCP 探活判孤儿
- 骨干选路：jitter 选路 + endpoint-target；relay client/server/wire/identity/directory/rendezvous/switcher 调整
- 工作台 src/web/server.ts、src/worker/relay-tunnel.ts 装配与候选链观测

脚本与测试
- scripts/overlay-{probe,keyring,jitter}.cjs 更新
- 探针新增 OBS-21（每连接候选数）/ OBS-22（teardown 静态守卫 + 认领面）/ OBS-23（组密钥加密）
- 新增 test/{orchestrator-teardown,orchestrator-rehydrate,overlay-content,overlay-jitter}.test.mjs；relay 两例更新

文档
- 新增交接单：覆盖网络-序24-内容分发块级寻址 / 序25-实例逐步拉起 / 序26-骨干稳定选路与加密
- INDEX.md、交接单/README.md、skills/dsh-auto-handoff-chain/SKILL.md 同步

验收（零回归，2026-09-18 08:0x 复核）
- npm test           201 tests / 200 pass / 0 fail / 1 skipped
- overlay-failover-drill --scene all --table   12 PASS / 0 SKIP / 0 FAIL
- overlay-probe --table                        23 PASS / 0 SKIP / 0 FAIL (rc=0)

package.json

@@ -24,7 +24,7 @@
     "typecheck": "tsc -p tsconfig.json --noEmit",
     "check:layering": "node scripts/check-layering.mjs",
     "verify": "npm run build && node scripts/check-layering.mjs && node --test test/db.test.mjs test/local-user-fs.test.mjs test/remote-user-fs.test.mjs test/crash-policy.test.mjs test/locale-pref.test.mjs test/worker-provision.test.mjs test/reachability.test.mjs test/instance-port.test.mjs test/relay.test.mjs test/remote-spawner.test.mjs test/overlay-network.test.mjs test/overlay-auth.test.mjs test/overlay-bootstrap.test.mjs && node scripts/verify-inject.cjs lib/supervisor/proxy.js && node scripts/verify-static.mjs && node scripts/verify-platform-admin-section.mjs && node scripts/verify-mem-model.mjs && node scripts/verify-model-landing.mjs && node scripts/verify-dsh-install.mjs && node scripts/verify-models-dict.mjs && node scripts/verify-models-render.cjs && node scripts/verify-dsh-compat.mjs && node scripts/verify-my-skills.mjs && node scripts/verify-portal-entry.mjs",
-    "test": "npm run build && node --test test/db.test.mjs test/local-user-fs.test.mjs test/remote-user-fs.test.mjs test/crash-policy.test.mjs test/reachability.test.mjs test/instance-port.test.mjs test/relay.test.mjs test/remote-spawner.test.mjs test/overlay-network.test.mjs test/overlay-auth.test.mjs test/overlay-bootstrap.test.mjs test/overlay-identity.test.mjs test/relay-failover.test.mjs && node scripts/verify-inject.cjs lib/supervisor/proxy.js",
+    "test": "npm run build && node --test test/db.test.mjs test/local-user-fs.test.mjs test/remote-user-fs.test.mjs test/crash-policy.test.mjs test/reachability.test.mjs test/instance-port.test.mjs test/relay.test.mjs test/remote-spawner.test.mjs test/overlay-network.test.mjs test/overlay-auth.test.mjs test/overlay-bootstrap.test.mjs test/overlay-identity.test.mjs test/relay-failover.test.mjs test/overlay-jitter.test.mjs && node scripts/verify-inject.cjs lib/supervisor/proxy.js",
     "smoke": "node scripts/smoke.mjs",
     "smoke:admin": "node scripts/smoke-admin.mjs",
     "smoke:auth": "node scripts/smoke-auth.mjs",