refine: Add 'ask-matt' skill and update documentation for user-invoked skills

skills/engineering/ask-matt/SKILL.md

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+---
+name: ask-matt
+description: Ask which skill or flow fits your situation. A router over the user-invoked skills in this repo.
+disable-model-invocation: true
+---
+
+# Ask Matt
+
+You don't remember every skill, so ask. Describe where you are — "I've got a vague idea", "bugs are piling up", "this code's a mess" — and this answers with the **flow** to follow and the skill to type next.
+
+A **flow** is a path through the skills. Most paths run along one **main flow**, and two **on-ramps** merge onto it. Everything else is standalone.
+
+## The main flow: idea → ship
+
+The route most work travels. You have an idea and want it built.
+
+1. **`/grill-with-docs`** — sharpen the idea by interview. Start here when you **have a codebase**: it's stateful, retaining what it learns in `CONTEXT.md` and ADRs. (No codebase? Use `/grill-me` — see Standalone.)
+2. **Branch — can you settle every question in conversation?** If a question needs a runnable answer (state, business logic, a UI you have to see), detour through a prototype, bridged by **`/handoff`** in both directions (see Crossing sessions):
+   - **`/handoff`** out, then open a fresh session against that file,
+   - **`/prototype`** to answer the question with throwaway code,
+   - **`/handoff`** back what you learned, and reference it from the original idea thread.
+3. **Branch — is this a multi-session build?**
+   - **Yes** → **`/to-prd`** (turn the thread into a PRD) → **`/to-issues`** (split the PRD into independently-grabbable issues) → **`/implement`** the issues one by one, each in its own agent.
+   - **No** → **`/implement`** right here, in the same context window.
+
+### Context hygiene
+
+Keep steps 1–3 in **one unbroken context window** — don't compact or clear until after `/to-issues` — so the grilling, PRD, and issues all build on the same thinking. Each `/implement` then starts fresh, working from the issue.
+
+The limit on this is the **[smart zone](https://www.aihero.dev/ai-coding-dictionary/smart-zone)**: the window (~120k tokens on state-of-the-art models) within which the model still reasons sharply. If a session approaches it before `/to-issues`, don't push on degraded — `/handoff` and continue in a fresh thread.
+
+## On-ramps
+
+A starting situation that generates work, then merges onto the main flow.
+
+- **Bugs and requests piling up** → **`/triage`**. It moves issues through triage roles and produces agent-ready issues, which **`/implement`** later picks up.
+
+## Codebase health
+
+Not feature work — upkeep.
+
+- **`/improve-codebase-architecture`** — run whenever you have a spare moment to keep the codebase good for agents to operate in. It surfaces deepening opportunities; picking one *generates an idea* you can take into the main flow at `/grill-with-docs`.
+
+## Crossing sessions
+
+- **`/handoff`** — when a thread is full or you need to branch off (e.g. into a `/prototype` session), this compacts the conversation into a markdown file. You don't continue in place — you **open a new session and reference that file** to carry the context across. It's the bridge between context windows, in either direction. Use it when you want a **fresh session** but need the **current conversation preserved**.
+- **`/compact`** (built-in) — stay in the **same conversation**, letting the earlier turns be summarized. Use it at **intentional breaks between phases**, when you don't mind losing the verbatim history. Don't compact mid-phase — the agent can lose its way. `/handoff` forks; `/compact` continues.
+
+## Standalone
+
+Off the main flow entirely.
+
+- **`/grill-me`** — the same relentless interview as `/grill-with-docs`, but for when you have **no codebase**. Stateless: it saves nothing locally, builds no `CONTEXT.md`. Reach for it to sharpen any plan or design that doesn't live in a repo.
+- **`/teach`** — learn a concept over multiple sessions, using the current directory as a stateful workspace.
+- **`/writing-great-skills`** — reference for writing and editing skills well.
+
+## Precondition
+
+**`/setup-matt-pocock-skills`** — run once per repo before any engineering flow. It configures the issue tracker, triage labels, and doc layout the other skills assume.