[Stamina9]

What does this change?

Convert FreeMASTER oscilloscope TXT exports to CSV. The sample in #571 contains a # Oscilloscope Data marker, a tab-separated header and 29 columns of readings. The converter preserves each field as text, including empty fields and leading zeroes.

This is deliberately limited to identified FreeMASTER exports: ordinary TXT and files with inconsistent column counts are refused with an explanatory error. The new TXT → CSV edge is direct-only so it does not change existing multi-step text routes. The existing CSV preset is offered on the text donut; schema 55 adds it to existing profiles when a slot is available and the user has not placed it already.

Addresses #571.

Type of change

• Bug fix
• New feature or improvement
• New format or engine
• Translation
• Documentation
• Build, CI or dependencies

How was it tested?

• dotnet format Filee.slnx --verify-no-changes --no-restore
• New generated fixtures cover UTF-8 / UTF-16, quoted text, Unicode, empty fields, malformed column counts and ordinary text; the conversion tests failed before the change and pass afterward.
• Converted the issue sample with Filee CLI on Windows: all 116 CSV rows and 29 columns matched the source cells. The source sample is not committed.
• Full local run so far: Core 718 passed (3 skipped), Platform 86 passed (28 skipped), CLI 39 passed (1 skipped), Engines 1893 passed (192 skipped), Setup 196 passed.
• App suite still running locally; CI will also run the full suite.

Screenshots (UI changes)

The existing CSV preset is added to the text donut back face; no new UI strings.

Checklist

• No new UI strings
• No new third-party code or binaries
• The PR does one thing

[KnifeLemon]

Thanks, @Stamina9! The converter and its tests are good. One change: the CSV slot on the text donut would show for every .txt file and fail for anything that isn't a FreeMASTER export, so I've left the default slot and the schema 55 step out.

This branch doesn't allow edits from maintainers, so I've carried your commit over unchanged (you stay its author) with that change on top in #721, and I'm closing this one in favour of it.