Error when someone drops a .tsv file (or similar non fasta-like) into sequence box

[corneliusroemer]

Just noticed that one can drop a .tsv file into the sequences box and it doesn't error:

On this page: https://pathoplexus.org/mpox/submission/232/revise?inputMode=bulk

[claude]

This issue appears to be related to #2922, which tracks incorrect validation messages for FASTA sequence upload errors. Both issues involve file validation problems in the sequence upload component, though they describe different aspects of the problem:

• Incorrect validation messages for FASTA sequence upload errors #2922: Incorrect validation messages when a malformed FASTA file is uploaded
• This issue: No error when a completely wrong file type (e.g., .tsv) is uploaded

These may benefit from being addressed together as part of a comprehensive file validation improvement.

[theosanderson]

I'd be cautious about being too fussy about filenames, but I guess we could error for XLSX and TSV