feat(bugs): add markdown richtext facets for bug descriptions
Add support for markdown formatting in bug descriptions and steps to reproduce:
- **bold** with **text**
- *italic* with *text* or _text_
- `inline code` with backticks
- ```fenced code blocks``` with optional language
Implementation:
- New lexicon: network.slices.tools.richtext.facet with bold/italic/code/codeBlock/link types
- Parser detects markdown syntax and creates facets (delimiters preserved for editing)
- Renderer strips delimiters and outputs formatted HTML
- GraphQL queries updated to fetch __typename for facet type detection
- CSS styles for all formatting types
- Form hints show supported syntax