v0.3.0-beta.0

BREAKING: Shell to Python migration + Command namespace changes.

Shell Scripts to Python

All .sh scripts replaced by .py equivalents. Requires Python 3.10+.

Commands moved to namespaced paths:

Platform	Old	New
Claude Code	`.claude/commands/start.md`	`.claude/commands/trellis/start.md`
Cursor	`.cursor/commands/start.md`	`.cursor/commands/trellis-start.md`

Run trellis update --migrate to apply changes.