Implement a taskforge task against its active Specification and emit only the implementation — the build half of the split run workflow (docs/ADR-0001 Phase 6). Use when a task's readiness is "run" (ready to build). Produces one implementation artifact; it does NOT review its own work — an independent taskforge-review follows. Escalates upstream defects (spec unimplementable, approach wrong, spec premise provably false) instead of pushing through. Tasks without an active specification route to taskforge-refine.
