Small fix: `implement`'s first line doesn't cover the same-session path that `ask-matt` documents

# `implement`'s first line doesn't cover the same-session path that `ask-matt` documents `ask-matt`'s main flow, step 3, explicitly endorses running `/implement` without a spec or tickets: > **Branch — is this a multi-session build?** > - **No** → **`/implement`** right here, in the same context window. This is a very common path: after a few rounds of `/grill-me` or `/grill-with-docs`, the task turns out simple and the context is still small, so you implement right there — the plan lives in the conversation, not in a file. But `implement`'s SKILL.md only knows about specs and tickets: > Implement the work described by the user in the spec or tickets. So the skill nudges the model toward hunting for a spec/ticket file (or asking for one) instead of implementing what was just agreed in the thread. ## Suggested fix One line: > Implement the work described by the user — in the spec, tickets, or the conversation so far. Optionally mention the same-session path in `docs/engineering/implement.md` too, so it matches ask-matt.