[REQ-128][CODE] 安装并预检 managed OpenCode Plugin artifact

[jinjunnn]

Outcome

消费alpha-web签名managed Plugin artifact，经CAS strict wrapper与授权后的pre-switch packaged
engine probe安装OpenCode V1 Plugin；Catalog-managed路径绝不进入runtime Npm.add。

Covers

alpha-work#49 AC2/AC5/AC6/AC7。

Solution baseline

Accepted REQ-128 baseline
§1.3、§2.7–§2.9。

Boundary and development plan

1. pin#97/feat(ui-mac): REQ-038b 会话页 slash 弹框与首页统一(alpha 菜单组件级接管) #99 managed Plugin profile/corpus；严格验source provenance、artifact/file digest、
   runtime/platform、无native/install-script dependency。
2. materialize到现有CAS，生成Alpha strict V1 wrapper；managed loader禁止legacy arbitrary
   function export fallback。
3. #713授权后、config switch前启动同版本packaged engine probe subprocess：
   strict import、V1 init、bounded dispose/cancel。
4. timeout/throw/ABI不符使transaction pre-switch失败；旧config从未切换。
5. probe成功才switch + [REQ-128][CODE] 切换 BundleGraph V3 ledger、claim set 与全部 writer #706 mutation；同包npm/vendored/local/legacy双载拒绝。
6. UI/授权始终披露“同权限engine-process code”；network/files/process仅declared/observed，
   不伪装sandbox。
7. unmanaged用户npm/path escape hatch保留但不标managed/verified。

Acceptance and named gates

• ABI corpus：合法V1、legacy-only、未知ABI、invalid dispose/cancel、double export/load。
• producer tarball/closure、signed file table、Desktop CAS三层tamper negatives。
• production wiring断言managed entry不调用Npm.add。
• candidate probe timeout/throw/ABI fail都在switch前；旧version继续健康。
• packaged evidence：install→restart→hook/tool→failed pre-switch update→old healthy→uninstall。

Dependencies

Blocked by alpha-web#97、alpha-web#99、alpha-code#713。

Out of scope

native module、post-commit automatic rollback、通用sandbox、静态行为证明、hook格式直译。

Exit condition

Merged PR + security review + ABI/integrity/probe/packaged evidence + runtime docs。