⚗️ Add canvas change detection for Session Replay

[BeltranBulbarellaDD]

Motivation

Canvas image capture can be expensive, so Session Replay should only capture a canvas after its contents have changed. This stacked PR adds the dirty-state pre-filter foundation for canvas recording.

Depends on #4947.

Design references:

• One Pager: Session Replay Canvas Support
• Browser SDK Canvas Support

Changes

• Add a WeakSet-backed canvas manager to track dirty canvases without retaining detached elements.
• Instrument bitmap-mutating CanvasRenderingContext2D methods and canvas width/height changes.
• Enable canvas mutation tracking only when canvas recording is enabled with a positive maximum frame rate.
• Safely handle canvas APIs that are unavailable in older browser versions.
• Add focused unit coverage for dirty-state management, canvas instrumentation, cleanup, and recorder activation.

This PR only adds change detection; capturing and marking canvases clean will be connected in a follow-up.

Test instructions

yarn test:unit --spec packages/browser-rum/src/domain/record/canvas/canvasManager.spec.ts --spec packages/browser-rum/src/domain/record/trackers/trackCanvas.spec.ts --spec packages/browser-rum/src/domain/record/record.spec.ts
yarn typecheck

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	N/A	181.25 KiB	N/A	N/A	N/A
Rum Profiler	N/A	8.43 KiB	N/A	N/A	N/A
Rum Recorder	N/A	22.25 KiB	N/A	N/A	N/A
Logs	N/A	57.50 KiB	N/A	N/A	N/A
Rum Salesforce	N/A	139.20 KiB	N/A	N/A	N/A
Rum Slim	N/A	139.19 KiB	N/A	N/A	N/A
Worker	N/A	22.96 KiB	N/A	N/A	N/A
Rum Shopify	N/A	202.13 KiB	N/A	N/A	N/A
Rum-shopify Profiler	N/A	8.43 KiB	N/A	N/A	N/A
Rum-shopify Recorder	N/A	3.72 KiB	N/A	N/A	N/A

[datadog-datadog-prod-us1]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 87.50%
• Overall Coverage: 77.21% (+0.03%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: ad260aa | Docs | Datadog PR Page | Give us feedback!}

[BeltranBulbarellaDD]

@codex review

[chatgpt-codex-connector]

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