parse_song_run: fix view counts misparsed as artist in CJK locales

[Rishi943]

Fixes #952.

parse_song_run() classified a non-linked run as a view count only when it matched ^\d([^ ])* [^ ]*$ — i.e. it required an ASCII space between the number and the "views" word. CJK locales don't have one: with language="ja", view counts arrive as e.g. "3406万回視聴", so the run fell through to the else branch and was returned as a bogus unlinked artist alongside the real one.

Fix, keeping the existing heuristics' spirit:

• Check the fully-specific patterns first: duration ((\d+:)*\d+:\d+) and year (^\d{4}$) — unchanged.
• Then treat any remaining digit-leading run as views. Only split off the first token when a space is actually present; for scriptio-continua locales the full text is kept as the views value (there's no safe way to split the magnitude from the "views" word, and dropping it would lose information).

Digit-leading unlinked artist text was already matched by the old views regex in the common "21 Savage"-shaped case, so this doesn't introduce a new misclassification class — linked artist runs (with navigationEndpoint) are unaffected either way.

Verified against the runs from the issue (ヨルシカ + 3406万回視聴 + 3:48):

{'artists': [{'name': 'ヨルシカ', 'id': 'UC...'}], 'views': '3406万回視聴', 'duration': '3:48', 'duration_seconds': 228}

Regression-checked: "34M views" → 34M, non-breaking-space variant, "1,234,567 views", "2020" (year), "3:48"/"1:23:45" (duration), and the unlinked-artist fixture case "The Wolfpack & Reel Wolf" (still artist — doesn't start with a digit).

Note: written with AI assistance (Claude Code); verification outputs above were produced by running parse_song_runs directly on the issue's data.