Fixed issue on temporary folder

[kreamweb]

Proposed changes

Fixes unreliable behavior around the editor chat temporary upload directory (uploads/nfd-chat-temp/), which is used by POST /nfd-editor-chat/v1/upload and read by MCP DocumentRead.

Problems addressed

• nfd-chat-temp/ was only created on the first successful upload, so consumers (e.g. MCP document read via realpath()) could fail when the directory did not exist yet.

• Upload validation relied on the browser-reported MIME type ($file['type']), which is often application/octet-stream for .csv, .md, and .pdf on production hosts.

• ChatEditor was only bootstrapped when Permissions::is_editor() was true at plugins_loaded, so REST routes were not registered in some request contexts.

Changes

• Always bootstrap ChatEditor from Application; gate editor UI hooks (assets, admin bar, canvas styles) behind Permissions::is_editor().
• Add ensure_temp_upload_dir() on init to create nfd-chat-temp/ early, with a guard index.php.
• Validate uploads by allowlisted extension + wp_check_filetype(), with a fallback when the browser sends application/octet-stream.
• Centralize temp path helpers (TEMP_UPLOAD_SUBDIR, get_temp_upload_paths()).
• Harden Application bootstrap when plugins_loaded has already fired; prevent double initialization.
• Update wpunit coverage for REST route registration, directory creation, and CSV/octet-stream acceptance.

Production

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Dependency update
• Refactoring / housekeeping (changes to files not directly related to functionality)

Development

• Tests
• Dependency update
• Environment update / refactoring
• Documentation Update

Visual

Checklist

• I have read the CONTRIBUTING doc
• I have viewed my change in a web-browser
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments