Add Grill discovery-interview workflow to the ISA skill

[asdf8675309]

The gap

ISA already covers known-structure work — Scaffold, Interview, CheckCompleteness, Reconcile, Seed, Append. What's missing is the front end for when you don't know the shape yet. If an idea's still half-formed, you can't scaffold it honestly — you just bake in assumptions nobody checked. That's the most common way agentic work goes off the rails: the agent runs with the wrong mental model before you get a chance to correct it.

The change

A Grill workflow that interrogates a half-formed idea until its shape is clear, then hands it to Scaffold. Three pieces:

• skills/ISA/Workflows/Grill.md — walks the design tree one question at a time, recommends an answer each turn, explores the codebase instead of asking when it can, and checkpoints every turn to MEMORY/WORK/{slug}/grill.md so a long session doesn't lose earlier answers to context drift. Runs a pre-mortem→draft-ISC pass, then hands off to Scaffold.
• skills/ISA/SKILL.md — one new routing row ("grill me" / "discovery interview" / "figure out the shape" → Workflows/Grill.md) and a Grill clause in the description.
• commands/grill-me.md — a thin /grill-me <topic> command that routes into Skill("ISA", "grill me …"). Model-invocation is off, so it only fires when you ask.

Same split as the skill it's based on: a reusable interview loop plus a thin command to trigger it.

Why it's safe

• Additive. One new workflow, one new command, one routing row, one description tweak. Nothing existing changes.
• Fails safe. If Grill mis-routes it falls back to normal ISA behavior, and it never writes outside MEMORY/WORK/{slug}/grill.md — scratch output that sits next to where the ISA lands.
• Human-gated. The command is disable-model-invocation; Grill runs only when you call it.

Verification

• Running live in a real install: commands/grill-me.md → Skill("ISA", "grill me …") → the SKILL.md Grill row → Workflows/Grill.md, all resolve. The ISA skill validates — every routing row points at a real file, and the description is under the frontmatter cap.
• The Grill → Scaffold handoff works end to end: the grill.md checkpoint feeds Skill("ISA","scaffold from <slug>/grill.md").

Scope

Additive. Workflows/Grill.md and commands/grill-me.md are new, plus two small edits to ISA/SKILL.md. No other skill, tool, or hook touched.

Credit

This adapts Matt Pocock's grilling / grill-me skills (github.com/mattpocock/skills — MIT, © 2026 Matt Pocock). His "grill me" prompt is the core idea: interview me relentlessly about every aspect of this plan; walk each branch of the design tree, resolving dependencies one at a time; recommend an answer per question; ask one at a time; explore the codebase instead of asking. This is an independent implementation wired into LifeOS's ISA discovery→scaffold pipeline — it checkpoints each turn to MEMORY/WORK/{slug}/grill.md instead of a project-root brainstorms/ folder, and adds a pre-mortem→draft-ISC pass before the Scaffold handoff.