Remove direct `chrono` usage without `jiff`

[zmrdltl]

Goal

• Remove direct chrono usage
• Do not add jiff

Scope

• list_files
• Simplify list_files and remove chrono #616

Acceptance Criteria

• Simplify list_files and remove chrono #616 complete
• No direct chrono usage in Cargo.toml, src, tests
• No jiff dependency

[zmrdltl]

I am assigning this to myself for review before proceeding.

[sophie-cluml]

This issue and sub-issues look good to me. @zmrdltl if you agree, could you have octoaide work on this and the sub issues please?

[zmrdltl]

I agree with octoaide taking this on. I’ll unassign myself so the work can proceed. @octoaide, please go ahead with the implementation, but only for the sub-issues listed here.

[sae-bom]

@sophie-cluml @zmrdltl

Question: do we still need list_files to return modified times?

The helper is private now, and current callers only use the filename field. The size and modified-time fields look like leftover API shape from when roxy exposed list_files publicly for other crates.
If no planned caller needs that metadata, simplifying this to return only file names would remove the modified-time lookup and roxy's direct chrono usage instead of migrating this code to jiff.

[sophie-cluml]

Thank you for the point out. It seems to me that all callers in prod code is not using the returned formatted datetime string at all. It seems more reasonable to me that we remove chrono dependency. I don't see the need to bring in jiff to roxy after the removal.