test: stabilize activity list pagination

[chaptersix]

Related issues

N/A

What changed?

Make TestActivity_List_Pagination exercise a deterministic mix of three completed and two running standalone Activities.

The test now waits for completed results, blocks running Activities until pagination finishes, and waits for visibility to report the exact status mix before listing. It also verifies each Activity appears exactly once with the expected status, avoiding the race where an Activity could complete and move in visibility ordering between page requests.

Checklist

Stability

• No user-facing behavior or output changes

Tests

• Updated functional test (SharedServerSuite)
• Focused pagination test passed 20 consecutive runs
• Neighboring Activity list/count tests passed

Testing

go test ./internal/temporalcli -run 'TestSharedServerSuite/TestActivity_List_Pagination$' -count=20
go test ./internal/temporalcli -run 'TestSharedServerSuite/TestActivity_(List(_Pagination)?|Count)$' -count=1
git diff --check