Expand a shell into a full implementation plan. Verifies Consumes against the current codebase, runs a fresh pattern survey, escalates open questions, and fills in concrete file references and verification. Use when the user asks to \"expand a shell\", \"expand shell\", \"fill in the shell\", \"expa
Expand a shell into a full implementation plan. Verifies Consumes against the current codebase, runs a fresh pattern survey, escalates open questions, and fills in concrete file references and verification. Use when the user asks to \"expand a shell\", \"expand shell\", \"fill in the shell\", \"expand the shell\", or \"concretize the shell\".