fix(lyrics): drop LRC header tags and read short fractions as milliseconds

[devtechedge]

[ar:Queen] and [offset:+500] were kept as lyric lines. parse_synced_lyrics read the minutes, seconds, and fraction with unwrap_or(0), so a tag that is not a number became a blank row at 0. [offset:+500] was worse: Rust's u64 parser accepts +500, so that tag became a blank line at 8:20. active_lyric_index stops at the first later timestamp, so the highlight stuck on that blank line for most of the song.

A non-numeric minute, second, or fraction now drops the line. Header tags are gone. A timed line with empty text stays, so [01:00.00] is still an instrumental gap. [offset:] is not applied, the lines are not sorted, and a line with several stamps is not expanded.

A one-digit fraction was read as thousandths. [00:12.5] was 12.005 seconds. It is now 12.5 seconds: one digit times 100, two digits times 10, three digits unchanged. A fraction longer than three digits used to be added raw, so [00:01.1234] was 2.234 seconds. It now keeps the first three digits, 1.123 seconds. That change is on purpose.

A body that is only tags parses to nothing, so the existing plain-lyrics fallback in apply_lyrics_response runs. No extra branch for that.

• lrc_metadata_tags_are_not_lyric_lines
• an_lrc_offset_tag_is_not_a_line_at_eight_minutes
• a_one_digit_lrc_fraction_is_tenths_of_a_second
• an_lrc_fraction_past_three_digits_keeps_the_milliseconds
• synced_lyrics_of_only_lrc_tags_fall_back_to_plain_lyrics

Checked locally:

• cargo test --no-default-features --features telemetry,tui lrc_: 5 passed, 1461 filtered out
• cargo fmt --all -- --check
• cargo clippy --no-default-features --features telemetry,tui -- -D warnings
• cargo test --no-default-features --features telemetry,tui: 1466 passed, 0 failed

Fixes #673

Summary by CodeRabbit

• Bug Fixes
  • Synced lyrics no longer display LRC metadata and offset tags as blank lyric lines.
  • Timestamp fractions are interpreted more accurately: one digit represents tenths of a second, two digits are scaled to milliseconds, and longer values use the first three digits.
  • Invalid timestamp fields are no longer treated as zero, helping prevent incorrect lyric timing. When synced content contains only tags, lyrics fall back to plain text.

[coderabbitai]

📝 Walkthrough

Walkthrough

The synced-lyrics parser now drops malformed timestamp fields and scales fractional seconds to milliseconds. Tests cover LRC metadata tags, fractional precision, and fallback to plain lyrics when synced content contains only tags.

Changes

Synced lyrics parsing

Layer / File(s)	Summary
Timestamp parsing and validation src/infra/network/utils.rs, CHANGELOG.md	The parser rejects malformed minute, second, or fraction fields. One- and two-digit fractions are scaled to milliseconds, and longer fractions use their first three digits. Tests cover metadata and offset tags, fraction handling, and plain-lyrics fallback for tag-only synced lyrics. The changelog records these changes.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: 🔵 Low · up to 3776a

A malformed lyric timestamp can place a line at the wrong time. The impact is limited to such inputs, so the PR has a bounded merge risk.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title uses the valid conventional-commit prefix fix(lyrics):, clearly describes the LRC header-tag and fractional-timestamp fixes, and uses concise imperative wording.
Linked Issues check	✅ Passed	The changes satisfy the coding requirements in issue #673. parse_synced_lyrics drops invalid minute, second, and fraction fields. It scales one- and two-digit fractions correctly and truncates longe…
Out of Scope Changes check	✅ Passed	The pull request changes only src/infra/network/utils.rs and CHANGELOG.md. The source changes implement issue #673 and add its requested automated tests. The changelog entry documents the same beh…

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[codecov]

Codecov Report

❌ Patch coverage is 98.03922% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/infra/network/utils.rs	98.0%	1 Missing ⚠️

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[coderabbitai]

Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @src/infra/network/utils.rs:
- Around line 473-474: Update the timestamp parsing logic around `secs_parts` to
reject timestamps unless the seconds field has exactly one fractional part after
the period; malformed input such as `[00:01.5.bad]` must cause the line to be
dropped.

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Reviewing files that changed from the base of the PR and between 9265a6d and 3776a01.

📒 Files selected for processing (2)

• CHANGELOG.md
• src/infra/network/utils.rs

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[LargeModGames]

That two-period stamp was accepted before this PR too, and #673 scopes the fix to header tags and fractions. Leaving it out here.

[devtechedge]

Thanks for the merge, LargeModGames, and for keeping #673 scoped to the header tags and fractions. If you ever want the two-period timestamp case tightened, I'm happy to open a separate issue for it.