Reduce progress-only WebKit page-record churn

[duggal1]

Scope

Avoid rewriting page metadata and refreshing page activity timestamps on every WebKit progress-only update. Preserve per-page observer progress delivery, navigation-state changes, history and viewport updates, and stale sequence rejection. Add regression coverage.

Evidence / limitations

This removes a demonstrably redundant runtime write; no measured FCP improvement is claimed. The raw-WebKit-vs-Blink differences reported by the existing benchmarks remain outside this change.

Validation requested

Run native Swift build and AgentTests on a suitable macOS 27 SDK runner and the headed Aether application benchmark before merging. This environment cannot execute the native macOS application.

Summary by CodeRabbit

• Bug Fixes
  • Web page loading progress now stays accurate when updates arrive out of order.
  • Progress-only updates no longer incorrectly refresh a page’s last-active time.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Free

Run ID: 265ce854-ceb8-4986-a0b8-52767e073834

📥 Commits

Reviewing files that changed from the base of the PR and between c8b6729 and 7c9c7f1.

📒 Files selected for processing (2)

• Sources/EngineRuntime/WebKit/SystemWebRuntime.swift
• Tests/AgentTests/WebKitPerformanceTests.swift

Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

The runtime now avoids updating a page record and its last-active timestamp when incoming state changes only in progress. Tests verify that progress updates preserve the timestamp and that stale progress does not replace the observed value.

Changes

WebKit progress update handling

Layer / File(s)	Summary
Detect tracked changes and verify progress updates Sources/EngineRuntime/WebKit/SystemWebRuntime.swift, Tests/AgentTests/WebKitPerformanceTests.swift	The runtime checks viewport, URL, loading, content readiness, error, and nonempty history changes before updating the page record. When none change, it publishes page state and returns without updating the record or its last-active timestamp. Tests verify that progress-only updates preserve the timestamp and stale progress does not replace the observed value.

Estimated code review effort: 2 (Simple) | ~10 minutes

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Note

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