perf(desktop): skip duplicate browser updates - #8018

Eligibility
This is a localized preview performance optimization that removes redundant PiP IPC and desktop state publications while preserving recording cadence and handling delivery failures and renderer reloads. Production changes are small and supported by targeted tests, with no schema, deployment, security, billing, or product-default impact.

Notes:
No code owners found in target merge base ebb9b9f