fix(server): verify the native display viewport capture without a window resize - #22176

Eligibility
This is a focused server bug fix that makes viewport verification deterministic and removes a bounded screenshot retry workaround, with only a limited capture-timing change in the existing display path. It introduces no product-default, schema, infrastructure, security, billing, or static-analysis changes.

Notes:
No code owners found in target merge base 069e63b

Agent Credits: 30 credits
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