v0.3.0

Author attribution

• Author profiles live in authors/ as Markdown files with frontmatter
• bead author new, list, set, set-default subcommands
• New beads automatically get the default author from config
• Author pages rendered at /author/<slug> in built site and preview
• Per-bead author override via bead author set <bead> <author>
• AI author type supported (stores system prompt in frontmatter)