fix(cli): accept YouTube video IDs starting with a dash

[carlosacchi]

Fixes #599.

Problem

argparse treats any positional token starting with - as an unknown option, so a YouTube video ID with a leading dash makes the CLI error out:

$ youtube_transcript_api -X9P8VE94Po --format text
youtube_transcript_api: error: unrecognized arguments: -X9P8VE94Po

The existing \- escape works but is undocumented, and the -- separator does not help because it forces every following token (including flags) to be treated as a positional video ID.

Change

YouTubeTranscriptCli.__init__ now pre-escapes any incoming token matching the YouTube video ID pattern with a single leading dash:

^-[A-Za-z0-9_][A-Za-z0-9_-]{9}$

by prepending a backslash before argparse runs. The existing _sanitize_video_ids step strips that backslash after parsing, so the resulting video_ids list contains the original IDs.

The second character is required to be non-- so that long options such as --languages (which is also 11 characters long) are not misclassified as video IDs. Video IDs starting with -- are extremely rare and can still be passed using the existing manual \ escape.

Tests

Added test_argument_parsing__youtube_id_starting_with_dash_is_auto_escaped covering:

• -X9P8VE94Po --format text parses as video_ids=['-X9P8VE94Po'], format='text'
• Multiple dash-prefixed IDs followed by --languages de en parse correctly
• Normal IDs and options are unaffected

Existing test_argument_parsing__video_ids_starting_with_dash (manual \ escape) still passes.

Full CLI test suite: 23 passed, 1 skipped.