implement-spec

# Implement Spec Drive a whole spec to completion by looping over its task graph, one task end-to-end at a time. The artifacts do the coordination: `_tasks.md` supplies the order, each `task_NN.md` supplies the contract and carries the status, and this loop just walks the graph — which is why a killed loop resumes exactly where it stopped. **Invoking this skill is the authorization to run the whole loop.** Do not ask for confirmation, do not wait for further instructions, and do not present the plan as a question ("Please confirm and I'll start") — the human gates already happened: the breakdown was approved in `write-tasks`, and every task carries its own verification gate. A confirmation prompt here only stalls an AFK loop. ## 1. Resolve the spec `$ARGUMENTS` names the spec (slug or path under `docs/specs/`). Read `_prd.md`, `_techspec.md` if present, and `_tasks.md`. Parse the graph from the manifest frontmatter and the current `status` of every task file it lists — statuses live in the task files, never in the manifest. `--from task_NN` skips everything before that task (its `needs` must already be `completed`). ## 2. Plan the waves Topologically sort the graph: wave 1 = tasks with no `needs`; wave N = tasks whose `needs` are all satisfied by earlier waves. Tasks already `completed` are skipped — re-running the loop is idempotent. A task with a `failed` dependency is blocked, not skippable. Print the wave plan as a statement, not a question, and **start executing ...