Brownfield entry point for the V-Model workflow. Reverse-engineers an existing codebase into the standard V-Model artifacts: plan-context.md, ADRs, arc42 snapshot, FEATURE inventory, backlog seed, and an evidence-based BA draft. Walks the V backwards from Coding up to Business Analysis, filling every step only with what can be proven from the code or the existing documentation. Every claim is sourced (path:line or doc section); nothing is invented. Use this skill when the user mentions "existing project", "legacy codebase", "reverse engineer", "import existing code", "brownfield", "we already have code", "onboard existing project", or when the user wants to enter the V-Model workflow but artifacts do not exist yet.