Remove separate agent/workflow/skill directories (src/bmm/agents,
src/bmm/workflows, src/core/skills, src/utility/agent-components) and
reorganize all content into phase-based structures under src/bmm-skills
(1-analysis, 2-plan-workflows, 3-solutioning, 4-implementation) and
src/core-skills. Eliminates the agent/skill distinction by treating
agents as skills within their workflow phase.