Fix YAML front matter generation to handle special characters

[Copilot]

YAML front matter in generated concept files was using string interpolation, causing parse errors when concept names or tags contained special characters (:, ", {, [, #, etc.).

Changes

• Replace manual YAML string formatting with yaml.safe_dump() for proper escaping
• Add missing Counter import from collections

Before/After

# Before: breaks on "Concept: Example" or tags with colons
content = f"""---
title: {self.name}
tags: [{', '.join(sorted(self.keywords))}]
---"""

# After: proper YAML serialization
frontmatter = {
    'title': self.name,
    'tags': sorted(self.keywords),
    'hierarchy': hierarchy,
    'related': sorted(self.related_concepts)
}
yaml_str = yaml.safe_dump(frontmatter, default_flow_style=False, allow_unicode=True, sort_keys=False)
content = f"""---
{yaml_str}---"""

PyYAML is already in requirements.txt.

---

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