fix: align sourceFileVersions parsing with maxEmbeddedVersion

[mesutoezdil]

sourceFileVersions used strings.SplitN and skipped files without underscore, but maxEmbeddedVersion in runner.go uses fmt.Sscanf on any leading integer. this patch makes both consistent.

[Copilot]

Pull request overview

Aligns the CLI migration filename version parsing (sourceFileVersions) with the runtime embedded-migrations parsing (maxEmbeddedVersion) by accepting any .up.sql file whose filename begins with decimal digits, rather than requiring an underscore separator.

Changes:

• Updated sourceFileVersions to parse versions using fmt.Sscanf(name, "%d", &v) to match maxEmbeddedVersion behavior.
• Broadens recognized migration filenames from NNN_name.up.sql to any .up.sql filename with a leading integer.

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[EItanya]

@iplay88keys

[iplay88keys]

It would be good to align the approaches, but this is the wrong direction. If we go with this approach, something like 000007test.up.sql would be counted, but golang-migrate would silently skip that. The golang-migrate regex requires underscores, but skips any files that don't match that.

So I think the right approach would be to call golang-migrate's source.DefaultParse(name) directly to make sure that it can't drift.