feat(skills): add grill skill

Add a monorepo-owned grill skill and enable it at the repository root.

Remove stale craft-skill guidance that conflicted with pull-request follow-up commits.

.pi/skills/grill

@@ -0,0 +1 @@
+../../src/skills/grill

src/skills/craft-skill/SKILL.md

@@ -112,6 +112,5 @@ Finish when one branch matches the user's requested change.
 3. Report the result.
    List every changed path.
    State whether you enabled the skill or only authored it.
-   Do not stage or commit unless the user requested it.
 
    Finish when the user can review the exact files changed.

src/skills/grill/SKILL.md

@@ -0,0 +1,124 @@
+---
+name: grill
+description: Stress-test a plan, decision, or design through a one-question-at-a-time interview. Use when the user asks to grill, stress-test, pressure-test, challenge, interrogate, or poke holes in a plan.
+---
+
+# grill
+
+Interview the user until the session has no open questions.
+Open questions define the ending condition for the grill session.
+Blocked questions track known decisions with unsettled prerequisites.
+
+Do not begin implementation during or after grill without an explicit user instruction.
+A completed grill summary is not an instruction to build.
+
+## Run the interview
+
+1. Investigate first.
+   Read the conversation, files, and docs that can settle facts or reveal constraints.
+   Resolve factual questions yourself when tools can answer them.
+   Do not ask the user for facts you can find.
+
+   Finish when known facts, constraints, and unresolved decisions are visible.
+
+2. Build the open-question list.
+   Map the decisions needed to finish the grill session.
+   Include known dependent questions as blocked questions.
+
+   Finish when the list contains every known required question.
+
+3. Start the session.
+   Present the Open questions and Blocked questions sections in short form.
+   Include titles only, not full question bodies.
+   Format each item with the markers from [Open-question accounting](#open-question-accounting).
+   Then ask the first numbered question in the same turn.
+
+   Finish when the interview has started with exactly one numbered question.
+
+4. Run the question loop.
+   Show the Open questions and Blocked questions sections on every active grill turn.
+   Ask one numbered question at a time.
+   Apply [Question format](#question-format) to each question.
+   Wait for the user's answer.
+   Apply [Open-question accounting](#open-question-accounting) before asking again.
+   Resolve newly answerable facts yourself before asking again.
+
+   Finish when the answer is accounted for and the turn ends with a numbered question, summary, or pause statement.
+
+5. Close the interview.
+   Stop when the open-question list is empty.
+   Output a concise summary of every decision reached.
+   Include optional follow-up questions that were not added to the open-question list.
+   Do not act on the summary unless the user gives a new implementation instruction.
+
+   Finish when the summary is delivered and grill waits.
+
+## Question format
+
+End each active grill turn with exactly one numbered question.
+Give concrete options with trade-offs.
+Give a recommendation and rationale.
+
+Probe vague words, overloaded terms, and hidden assumptions.
+Use concrete scenarios to test concept boundaries and edge cases.
+When code contradicts the user's claim, quote both the claim and the code behavior.
+
+## Open-question accounting
+
+Show ready questions under `Open questions:`.
+Show questions with unsettled prerequisites under `Blocked questions:`.
+Use Markdown list items in both sections.
+Indent cause notes by two spaces under the changed question.
+Do not nest questions under other questions.
+
+Use the bracket marker to show item changes on the current turn:
+
+- `- [ ]` for unchanged unresolved questions
+- `- [+]` for questions added by the latest answer
+- `- [u]` for questions updated by the latest answer
+- `- [x]` for questions resolved by the latest answer
+- `- [-]` for questions removed by the latest answer
+
+Keep `- [ ]` items visible every turn.
+Show `- [+]`, `- [u]`, `- [x]`, and `- [-]` for one turn only.
+After that turn, keep an updated question visible as `- [ ]`.
+After that turn, remove resolved and removed questions from the visible list.
+
+When a blocked question becomes ready, move it to `Open questions:` with `- [u]` for one turn.
+Do not use `- [+]` for unblocked questions because they are not new.
+
+Add questions only when the latest answer directly causes them.
+When the user extends scope instead of answering, account for the new question before pursuing it.
+Do not add optional follow-up questions to the open-question list.
+Put optional follow-up questions in the final summary instead.
+
+Include a cause note for each `- [+]`, `- [u]`, and `- [-]` change.
+Use this format:
+
+```md
+Open questions:
+
+- [u] Copyleft preference
+  Cause: The `src/skills/` exception leaves the rest of the monorepo under the root license.
+
+Blocked questions:
+
+- [+] Patent explicitness
+  Cause: Your answer made patent terms relevant to the license choice.
+```
+
+Preserve agent judgment when the user reframes or invalidates a question.
+Show the resulting list change instead of following a rigid reframe algorithm.
+
+When the user catches incorrect open-question handling, briefly explain the error.
+Then show the corrected open-question list.
+
+## Turn endings
+
+While grill is active, every assistant turn must end with exactly one of these items:
+
+- the next numbered question
+- the final decision summary
+- a plain statement that grill is paused because the user changed tasks
+
+If the turn includes a correction, file edit, apology, or explanation, still end with the next numbered question.