Allow note input without octave

[icalvo]

Summary

• Notes can now be entered without an octave (e.g., C or C# instead of C4). When the octave is omitted, all valid octave combinations within the instrument's range are tried and displayed as separate chords in the score.
• Added PitchClass type, NoteInput union type, tryParseInput(), isNote(), expandPitchClass(), and generateNoteCombinations() to the string-fingerings library.
• Configured npm workspaces so the website uses the local string-fingerings package during development.

Fixes #16

Test plan

• Type a note without octave (e.g., C) on violin -- score should display multiple chords (C4, C5, C6, C7).
• Type a mix of octave and non-octave notes (e.g., C G5) -- score should show combinations of C at valid octaves paired with G5.
• Type notes with all octaves specified (e.g., G3 D4) -- behavior should be unchanged from before.
• Verify MIDI input still works correctly (always produces notes with octaves).
• Verify scordatura and highest-stop inputs still require notes with octaves.
• Run npx vitest run in packages/string-fingerings -- all 63 tests should pass.
• Run vue-tsc --build --force in website -- no type errors.

[netlify]

❌ Deploy Preview for stringinstrumenttools failed. Why did it fail? →

Name	Link
🔨 Latest commit	71b6781
🔍 Latest deploy log	https://app.netlify.com/projects/stringinstrumenttools/deploys/69a76fcdb0e0960008b9b531