The AI city forecast hook still owned stream queueing and in-flight request dedupe after the first request-client pass. Moving that policy into scanTerminalClient keeps network concurrency, queued progress, and requestKey reuse in the request layer while leaving the hook responsible only for cached UI state and progress rendering.
Constraint: Preserve existing two-stream concurrency limit and queued user-facing progress copy.
Rejected: Move localStorage cache at the same time | cache policy should be separated from stream transport policy to keep this refactor reviewable.
Confidence: high
Scope-risk: narrow
Reversibility: clean
Tested: npm run build
Not-tested: Live multi-city SSE under production latency.
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