Merges the final step for FN-3309, adding a changeset to document the removal of pi install references. The changeset is the only file changed, completing the feature work.
Fusion-Task-Id: FN-3309
- Add bundled Fusion skill at packages/cli/skill/fusion/ with SKILL.md and reference docs
- Include workflow guides for task lifecycle, specifications, dashboard CLI, and task management
- Add reference docs for CLI commands, extension tools, capabilities, best practices, and patterns
- Add postinstall script to sync skill into ~/.pi/agent/skills/fusion on install
- Add skill-sync test coverage and changeset for minor version bump
