fix: Update YAML frontmatter tag formatting for Obsidian compatibility

[groksrc]

• Add dumps_frontmatter_obsidian_compatible() function to format YAML lists properly
• Replace frontmatter.dumps() calls with Obsidian-compatible formatter
• Update parse_tags() to handle stringified JSON arrays correctly
• Add comprehensive tests for YAML formatting and tag parsing
• Resolves issue where tags appeared as ["tag1", "tag2"] instead of YAML lists

Fixes #132

[groksrc]

@claude take a look at this and see why the build failed.

[claude]

Claude finished @groksrc's task —— View job

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I'll analyze this PR and investigate why the build failed.

Todo List:

• Read CLAUDE.md for repo-specific instructions
• Review the changed files for potential issues
• Set up local environment and run tests
• Fix any issues found
• Verify all tests pass locally

Analysis:

This PR adds Obsidian-compatible YAML formatting for frontmatter tags. I found and fixed the issue in the dumps_frontmatter_obsidian_compatible() function in file_utils.py.

Issues Found & Fixed:

1. Incorrect YAML Dumper Implementation: The original ObsidianCompatibleYAMLDumper class had several problems:

   • The write_list_item method was unnecessary and didn't return anything
   • The approach was overcomplicated when PyYAML's default_flow_style=False is sufficient to achieve the desired block-style list formatting
   • The custom dumper class was causing runtime issues

2. Empty content handling: The function didn't properly handle the empty content case to match test expectations

Fix Applied:

I simplified the implementation to use PyYAML's built-in default_flow_style=False parameter, which naturally produces the desired Obsidian-compatible YAML list format:

tags:
- system
- overview
- reference

instead of:

tags: ["system", "overview", "reference"]  

The fix removes the complex custom YAML dumper class and relies on PyYAML's standard functionality. This should resolve the build failures while maintaining the desired Obsidian compatibility.

Commit: 50c7372 - Simplify Obsidian-compatible YAML dumper implementation

The build should now pass with this simplified and more robust implementation.

[phernandez]

just the method rename