refactor: remove DOM compatibility types

[jderochervlk]

Tracking issue: #342

Summary

• replace the temporary DOMTree aliases from refactor: introduce DOMTree compatibility foundation #301 with the concrete recursive interface family
• move the remaining shared non-tree types into DOM
• update residual DOM, Canvas, observer, UI event, WebAudio, and test consumers
• delete DomTypes and MutationObserverTypes

Temporary state

• this PR removes the compatibility scaffolding accumulated by refactor: introduce DOMTree compatibility foundation #301 through refactor: define SVG interfaces locally #308; no DomTypes, MutationObserverTypes, or alias-backed DOMTree layer remains after it
• CSS and stylesheet types remain in broad DOM for one final layer; refactor: move CSS and stylesheets out of DOM #288 moves them to their owning modules
• physical source-folder ownership is still temporary until the follow-up Option 5 folder/feature stack

Review focus

• correctness of the concrete recursive DOM type graph
• residual consumer migrations and the absence of deleted compatibility references
• whether the large change remains behavior-neutral despite needing to land atomically

Verification

• npm run build
• npm test
• npm run format:check

[jderochervlk]

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[chatgpt-codex-connector]

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