refactor: consolidate File folder feature

[jderochervlk]

Tracking issue: #342

Stack context

Part 10 of the Option 5 folder-feature stack.

• Previous: refactor: establish Fetch folder feature #319
• Next: another dependency-clean domain folder

Review this PR as the incremental diff against #319.

Summary

• rename src/File to the target src/file folder
• merge the former File and Directory Entries modules into the complete File folder
• move FileList from the legacy DOM folder into File
• move BaseFileAndDirectoryEntries out of core and into File
• remove the separate WebAPI.FileAndDirectoryEntries source feature
• preserve WebAPI.File -> WebAPI.Event + File and add the merged interfaces to its public module list

Temporary state

• BaseFile remains in core because DOM.shareData directly references it; moving it here now would create a DOM -> File -> Event -> DOM cycle
• the final cleanup layer will decide whether to relocate shareData, keep the shared Blob/File records foundational, or introduce a justified slice
• the internal FileTypes and File and Directory Entries helpers remain inside the correct folder pending cleanup

Review focus

• complete File folder membership and removal of the extra consumer feature
• preservation of all flat File and directory-entry public modules
• the explicit reason for retaining BaseFile in core

Verification

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

[jderochervlk]

@codex

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. What shall we delve into next?

Reviewed commit: 5d18c5088d

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