[patch] Stop Pitch octaves wrapping into range, and reject whitespace or '+' in the octave

[matt-edmondson]

Fixes #307

What was wrong

• Pitch.TryParse and Pitch.Create(NoteLetter, Accidental, int octave) computed ((octave + 1) * 12) + letter + accidental in unchecked int. A huge octave wrapped back into 0..127: "C1073741823", "C2147483647" and "C-1073741825" all parsed as C-1, and the typed factory returned C-1 for those octaves instead of throwing.
• The octave was parsed with NumberStyles.Integer, which allows leading and trailing whitespace and a leading +. So "C 4 " and "C+4" parsed and then printed back as "C4", which breaks the canonical-text round trip.

Change (Semantics.Music/Pitch.cs)

• A private MidiOf(octave, letter, accidental) computes the MIDI number in long, so no octave can wrap. Both TryParse and the typed Create use it before the 0..127 range check. I chose long arithmetic over a hard-coded octave window so the range check stays the only rule.
• Create(NoteLetter, Accidental, int) now throws ArgumentOutOfRangeException for an out-of-range result itself, naming octave. This is the documented exception type; before, it came from Create(int) naming midi.
• TryParse parses the octave with NumberStyles.AllowLeadingSign only, and rejects an explicit +. So a leading - (needed for octave -1) is the only thing accepted besides digits, and whitespace is rejected.

Tests (PitchTests)

• TryParse_RejectsWrappingOrNonCanonicalOctave: C1073741823, C-1073741825, C2147483647, C-2147483648, C 4, C 4 , C4 , C+4, plus C and C# with no octave.
• TryParse_AcceptsNegativeOctave: C-1 still parses to MIDI 0 and prints as C-1.
• Create_FromLetter_RejectsOctaveThatWouldWrap: 1073741823, int.MaxValue and int.MinValue throw ArgumentOutOfRangeException.

With Pitch.cs reverted, 11 of these cases fail. With the fix, the full Semantics.Test suite passes: 1494 passed, 0 failed, 8 skipped. Semantics.Music builds for every target framework.

TimeSignature and Velocity also parse with NumberStyles.Integer. I left them out of this PR to keep it scoped to the issue.

🤖 Generated with Claude Code

https://claude.ai/code/session_019RYN9jT6szUiySkywFKCA1

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Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

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