Resolve CSV file references with spaces against nested attachments

[SixtyGrit]

Summary

CsvParser#file_paths transliterates every file reference's spaces to underscores before checking existence (f.strip.tr(' ', '_')), while #remove_spaces_from_filenames only renames the top level of files/ — and the unzip_spec added with the guided importer (#1098) pins that one-level behavior deliberately, on the rationale that renaming nested entries would break CSV references.

Those two halves contradict each other for nested attachments: a CSV referencing files/subdir/photo name.jpg can never resolve — the lookup demands the underscored variant, the disk keeps the spaces, and the import aborts with RuntimeError: File ... does not exist.

This PR makes file_paths try the reference as written first, then fall back to the underscored variant (which still matches top-level files renamed by remove_spaces_from_filenames). No on-disk renaming behavior changes, so the #1098 spec's intent is preserved.

Real-world reproduction

Hit on a Hyku 7.1.x tenant importing a per-work-folder zip (files/<work-slug>/<photos>, the layout the CSV parser's parents/children conventions encourage) where four photos had spaces in their names:

RuntimeError - File tmp/imports/.../files/files/design-square-one/Square_1_Design.png does not exist

The file existed at .../files/files/design-square-one/Square 1 Design.png. Nothing in the importer UI or validation surfaces the mismatch; the run simply dies on the first spaced reference. Operators have no reason to expect underscores: the CSV they wrote matches the files they zipped.

Notes

A related observation from the same session, possibly worth a follow-up issue: the guided importer's upload validation passed this package, and the failure only surfaced later in ImporterJob — the validator and file_paths evidently resolve attachment paths differently. Happy to file separately with details.

Changes

• file_paths: candidate list [as-written, underscored], first existing wins; error message names the as-written reference.
• Specs: nested-spaces resolution (as-written) + top-level fallback (underscored) + error case.

🤖 Generated with Claude Code

[laritakr]

@SixtyGrit If this is something you need for Hyku, it also needs to be cherrypicked onto the 9-stable branch. Hyku isn't set up to use Bulkrax main yet (that includes Rob's changes that Pals brought up re: the export permissions)