Add a raw text output format

[omehegan]

When working on Support cases I've sometimes had the need to do offline parsing and analysis of job logs. The downloaded log files with included ANSI control characters make that difficult, but converting them to HTML is only one step better. When I mentioned this to @DrJosh9000 he pointed me at #146 and gave me some context around it. But he said he no longer had a need for the JSON output portion of that PR, and it's now so far behind main that it seemed easier to start fresh. This change adds an option to dump a log as raw text, and to include timestamps in that output if desired. That was all I needed.

Attribution: I used Claude to implement this change.

[DrJosh9000]

This is good, I think the main two improvements would be:

• support streaming mode with plain format
• support disabling timestamps with HTML format

If that's something you want to do, I'd be happy to wait, otherwise I don't mind doing it after merging this.

[omehegan]

@DrJosh9000 both suggestions make sense! I didn't think about streaming, but of course we should do that for plain. And with the timestamps, I made it so they're on by default in plain, as they already were in html. Then added --no-timestamps to optionally turn them off in either output format. LMK what you think.

[DrJosh9000]

Looks good! I have one suggestion