Grill the presentation product

Use when product-grill is the current gate.

• Read repo instructions, SOURCE-INVENTORY.md, and the cited source files before asking anything.
• Investigate discoverable answers in the sources instead of asking the user.
• Cover the full product model: audience, problem, outcome, promise, evidence threshold, constraints, visual direction & rendering DNA, success test, and out of scope.
• Mandatory Visual Theme Grilling: When visual direction or rendering style is unconfirmed, ask one focused question with concrete theme archetypes from themes/*.md or benchmark decks (e.g. sticker-pop / macau-wellbeing-sketch for physical sketch with 3px ink & hard shadows, bright-sans for Swiss minimal, aurora for dark glassmorphism). Never allow vague adjectives (e.g. "warm", "clean", "modern") to pass without binding them to a concrete rendering contract (border, shadow, typography scale).
• Before the first question, follow ../make-presentation/references/sharpen-playback.md: sharpen the task, write a one-paragraph ## Playback at the top of the brief, and proceed on recommended defaults (recorded as Assumed) for reversible choices.
• Grill in rounds per ../make-presentation/references/grilling-rounds.md when a consequential decision is still unresolved and the sources cannot answer it: ask the whole frontier (every decision whose prerequisites are settled) in one round, numbered, each with a recommended answer worded so "yes" accepts it. Never ask a question that depends on another open one in the same round. Honor "ask one question at a time" if the user requests it.
• Include a recommended answer with each question, worded so "yes" accepts it.
• Explain what the decision would invalidate downstream when that impact exists.
• Use references/autonomous-brief.md for the autonomous fallback when the user is unavailable (headless run) or the remaining product decisions are resolvable from the sources — resolve each open field with a defensible value, its rationale, and a confidence level (defaulting visual direction to an explicit registered theme from themes/*.md rather than generic unstyled UI), and flag any low-confidence load-bearing decision for later human review instead of silently guessing.
• Let any consequential change to Audience, Problem, Outcome, Promise, Evidence threshold, Constraints, Visual direction, Success test, or Out of scope invalidate downstream gates.

Write PRESENTATION-BRIEF.md from templates/PRESENTATION-BRIEF.md.

• Update the brief as soon as a question is resolved.
• Keep the brief decision-oriented and concrete.
• Prefer short sentences, explicit tradeoffs, and measurable success tests.

Write only consequential decisions to GRILL-LOG.md from templates/GRILL-LOG.md.

• Append new decisions without deleting or rewriting entries from other grill phases or earlier runs.
• Preserve existing decisions from story or stage grilling.
• Log decisions that materially change evidence, story, prototype, stage, or production work.
• Skip minor wording preferences and reversible drafting details.
• Stop once the brief is coherent enough for the evidence or story gate to proceed.