Fix session close retry on dynamic routes

[decofe]

Summary

• retry HTTP session close once when the stale close credential is rejected with a fresh 402 challenge
• sign the retry close credential against the newly advertised session challenge
• keep the existing WebSocket close flow unchanged

Validation

• corepack pnpm -C /home/agent/branches/wevm/mppx build
• corepack pnpm -C /home/agent/branches/wevm/mppx exec tsgo -b --pretty false
• targeted vp test src/tempo/client/SessionManager.test.ts was blocked by missing container runtime for the Tempo test server in this sandbox

Prompted by: @kazanins

[pkg-pr-new]

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npm i https://pkg.pr.new/mppx@487

commit: 8a6ad66