Attach some long code links in files

[00-kat]

I only special-case one code link as the context would then be directly above the file:

If it were done for all cases, the correspondence between contexts and files would not be apparent as the files are necessarily displayed at the end.

While I could do it for the last blob that causes the limit to be exceeded, that might end up being a two line snippet (for example); putting something that small in a file is odd.

[Copilot]

Pull Request Overview

This PR refactors the message editing hook and code snippet formatting to better support attaching long code links as files when necessary. Key changes include:

• Refactoring create_edit_hook by removing the embed_mode parameter and introducing extract_content to handle content, files, and embeds.
• Updating related hooks in xkcd_mentions and GitHub integrations to work with the new API.
• Adjusting code link formatting to special-case long single snippets by uploading them as files instead of embedding the entire content.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
app/utils/hooks.py	Refactored create_edit_hook to remove embed_mode and support files attachments.
app/components/xkcd_mentions.py & comments/integration.py	Removed embed_mode parameter from hook invocations.
app/components/github_integration/code_links.py	Modified snippet formatting to conditionally upload long snippets as files.