* fix(slack): reject HTML responses when downloading media
Slack sometimes returns HTML login pages instead of binary media when
authentication fails or URLs expire. This change detects HTML responses
by checking content-type header and buffer content, then skips to the
next available file URL.
* fix: format import order and add braces to continue statement
* chore: format Slack media tests
* chore: apply formatter to Slack media tests
* fix(slack): merge auth-header forwarding and html media guard
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Co-authored-by: Tak Hoffman <[email protected]>
