perf(hotspots): optimize DOM/Network paths and expand regression coverage

[lynnswap]

Summary:

• Optimize DOM auto-update snapshot flow to avoid unnecessary full snapshots and keep mutation bundles as the primary update path.
• Reduce Network buffering overhead by skipping request/response body capture while preserving metadata, queue behavior, and dropped-event accounting.
• Re-check network body-capture mode after async boundaries so in-flight requests honor active→buffering transitions.
• Batch network event application/resource timing handling to reduce main-thread churn.
• Add broad Swift and TypeScript regression coverage for DOM/Network hotspots, including quantitative acceptance checks.
• Keep execution guidance in README focused on local verification (swift test, npm run test:ts, npm run typecheck:ts).

Testing:

• swift test
• npm run test:ts -- --reporter=verbose
• npm run typecheck:ts

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

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Reviewed commit: aec370f5b1

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