Extract design decisions, trade-offs, and non-obvious behaviors from a codebase's current source code. TRIGGER when: starting the design analysis pipeline, running `/mine-design` (Claude Code) or `@mine-design` (Cursor) before `/synthesize-decisions` (Claude Code) or `@synthesize-decisions` (Cursor), capturing the reasoning behind current architectural choices, analyzing a codebase snapshot for patterns that would surprise a developer arriving cold.
