[REQ-087] LegacySessionAdapter feasibility spike

[jinjunnn]

Goal

给出 Layout/Session 拓扑、粗粒度 adapter 原型和 GO/NO-GO 证据。

Parent requirement

jinjunnn/alpha-code#202

Scope

• Deliver the jinjunnn/alpha-code boundary for Alpha REQ-087: LegacySessionAdapter feasibility spike.
• Preserve the parent requirement contract; do not absorb adjacent repository work.

Out of scope

• Work owned by sibling sub-issues or future REQs.

Acceptance criteria

• 实验不默认发布；输出依赖/滚动/焦点/命令/cleanup 矩阵。
• Relevant automated and packaged/runtime checks are attached before closure.

Dependencies

REQ-084 verified；REQ-005 是输入。

Verification evidence

• CI/test evidence.
• Security/runtime/product acceptance evidence appropriate to this repository.

[jinjunnn]

验收证据(S41,PR #239 已合并)

• ✅ 依赖拓扑矩阵/四方案比较/最小原型/边界决策/REQ-088 分解:docs/spikes/2026-07-12-req087-legacy-session-adapter.md
• ✅ 结论 CONDITIONAL GO,条件:C1 通道合法化(freeze-base 轮转加窄 ./surface/session export,先于 REQ-088)/ C2 真引擎 characterization(6 项 test.todo:长 timeline、终端生命周期、权限流、性能基线)/ C3 API 纪律(adapter props 全 alpha 窄类型,深导入锁单文件)/ C4 探针矩阵真机清零
• ✅ 实证:合法深导入通道不存在(exports map 无 ./pages/*);双挂载 command.register 键位互斥 = iframe/Portal 方案正确性反例;33 项 characterization 锚点测试入权威门
• ✅ 原型双通道均 flag 关闭零影响(release default session:legacy 有测试断言);真机探针 overlay 见 docs/audits/2026-07-12-s41-visual/22-spike-summary.png,summary 采样 6 次 1 次挂载违例(composer 0/1,ComposerTakeover 既有现状)已归入 C4
• 📌 按 REQ-087 AC#10:REQ-088 保持未激活直至 C1/C2 满足;实验代码未默认启用