Add FixType property to IFixCommonError

[ivandrofly]

Summary

• Add a FixType enum (Time, Formatting, Dialog, Punctuation, Casing, Spacing, Characters, Ocr) in src/libse/Enums.
• Add FixType FixType { get; } to IFixCommonError, so the compiler enforces it on every implementation.
• Every fix rule (39 in libse plus FixCommonOcrErrors in the UI) declares the kind of fix it performs, so the UI and CLI can group, filter or sort rules by category.

No behaviour change on its own; the first consumer is the "Type" filter in the Fix common errors window, stacked on this PR.

Test plan

• dotnet build SubtitleEdit.sln compiles (every IFixCommonError implementation has the new member)
• Spot-check a few classes: FixCommas is Punctuation, FixShortGaps is Time, FixUnneededSpaces is Spacing, FixCommonOcrErrors is Ocr
• dotnet test tests/libse/LibSETests.csproj passes

🤖 Generated with Claude Code

https://claude.ai/code/session_01SXEWrgv5uAnSzDgxFupSHZ

[niksedk]

Hi @ivandrofly, thanks for this! The categorisation itself is sensible, but I'm going to close it together with #14443: I'd like to keep the Fix common errors window as it is for now, so I don't want to add the FixType member to the interface and all 40 rule classes without a consumer for it. If a category filter ends up on the roadmap, the mapping you did here (rule -> type) is easy to pick up again.

Thanks again!