[REQ-089] Alpha route manifest and composition ownership

[jinjunnn]

Goal

实现 Alpha route manifest、composeRoutes、窄 runtime slots 与 ownership ledger。

Parent requirement

jinjunnn/alpha-code#204

Scope

• Deliver the jinjunnn/alpha-code boundary for Alpha REQ-089: Alpha route manifest and composition ownership.
• 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

• Web/MemoryRouter fixture、legacy aliases、导航单一来源和 semantic ledger 通过。
• Relevant automated and packaged/runtime checks are attached before closure.

Dependencies

REQ-085/086/088/090。

Verification evidence

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