Implement musical time conversion functionality (#25)

* spec: add comprehensive musical time conversion specification

- Define getMusicalTime() interface for converting real time to musical time
- Support arbitrary hierarchical depth with clear level naming
- Add optional referenceLevel parameter for fractional calculation at any hierarchy level
- Use pulse-based fractional calculation to handle rubato and irregular timing
- Include comprehensive test cases and edge case handling
- Designed for identical implementation across Python and TypeScript

* feat: implement musical time conversion functionality

- Add MusicalTime dataclass with cycle, hierarchical position, and fractional beat
- Add Meter.get_musical_time() method with optional reference level support
- Support arbitrary hierarchical depth (beat, subdivision, sub-subdivision, etc.)
- Use pulse-based fractional calculation to handle rubato and irregular timing
- Add comprehensive test suite with 18 test cases covering all functionality
- Update package exports for MusicalTime class
- Implement specification from docs/musical-time-spec.md

Features:
- Convert real time to musical position within meter boundaries
- Reference levels allow fractional calculation at any hierarchy level
- Handles complex meters like [3, 2, 4] with proper level naming
- Returns False for out-of-bounds times, MusicalTime for valid times
- String representations: compact (C0:2.1+0.500) and readable formats

* fix: remove duplicate Claude workflow to prevent multiple PR comments

- Removed claude.yml which was triggering alongside claude-code-review.yml
- Now only claude-code-review.yml handles @claude review comments
- This prevents duplicate comments on PR reviews

* fix: address Copilot review comment on array handling

- Fixed _calculate_level_start_time to properly handle truncated positions array
- Now correctly extends with zeros rather than potentially accessing out of bounds indices
- All tests still pass

* test: add comprehensive edge case tests for musical time conversion

- Added test for multi-level hierarchy overflow scenarios
- Added test for truncated positions array handling with reference levels
- Added test for recursive overflow at reference level boundaries
- Added test for complex list-based hierarchy overflow
- These tests specifically cover the edge cases Copilot's review identified
- All 22 tests pass, increasing confidence in robustness

Author: jon-myers