refactor: establish Geometry folder feature

[jderochervlk]

Tracking issue: #342

Stack context

Part 14 of the Option 5 folder-feature stack.

• Previous: refactor: establish Animation folder feature #323
• Next: another dependency-clean DOM-adjacent folder

Review this PR as the incremental diff against #323.

Summary

• add the target src/geometry folder on the unqualified internal Geometry feature
• move the DOM matrix, point, and rectangle interface families out of the legacy broad DOM folder
• add the supported WebAPI.Geometry feature with its WebAPI.DOM dependency
• preserve all seven flat public module paths and binding signatures

Temporary state

• the modules still use foundational DOM.* geometry records introduced by the earlier compatibility cleanup; the final cleanup layer will make the owning Geometry modules authoritative after all consumers move
• this PR introduces no exclusions or module slices
• DOMNodes, SVG, Observers, and Canvas dependencies on Geometry are added in their owning layers

Review focus

• complete Geometry folder membership
• the WebAPI.Geometry -> WebAPI.DOM + Geometry implication
• unchanged public interfaces

Verification

• node_modules/.bin/rescript clean
• node_modules/.bin/rescript build --prod --features DOM,Geometry
• npm run build
• npm test
• npm run format:check
• git diff --check

[jderochervlk]

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep the Geometry feature off the unbuildable DOM slice

When a consumer selects --features WebAPI.Geometry, the CLI transitively compiles implied features (as documented by rescript build --help), so this activates the broad source slice tagged WebAPI.DOM, not just the dependency-clean core DOM feature. That slice cannot currently compile selectively: DOMTree.res requires DOMStringMap from DOMPlatform, while TextTrackList.res requires EventTarget from Event, producing missing-module errors before any Geometry API can be used. The reported --features DOM,Geometry verification bypasses this new mapping; until the broad DOM slice is dependency-clean, this facade needs to imply DOM and Geometry directly or include all of the DOM slice's dependencies.

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