feat(hackmd-deck): add skill

Quick HackMD decks for light talks such as Agoric's engineering show &
tell: a flashback arc (TADA, then how, then challenges), real artifacts
as eye candy, and emoji tags that add up to a retro slide.

In the Portland Pattern Repository form notify-me tried, with an example
skeleton under the h1. The forces come from drafting the Good Fences
deck: the TADA has to be on the talk's own thread; slides show
challenges, they don't pose questions; designed, built in dev, and
deployed must be told apart.

The emoji legend is from the Jun 25 deck; meanings for 🔔 📈 🪄 are
inferred, and 🧱 is new.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

hackmd-deck/SKILL.md

@@ -0,0 +1,68 @@
+---
+name: hackmd-deck
+description: HackMD slide deck for a light talk — use when asked to draft slides, a deck, or a talk for show & tell, office hours, or a demo; when someone says "hackmd deck", "whip up some slides", or names a talk title and points at work to present (repos, git history, session transcripts). Covers the flashback story arc, emoji retro tags, and real artifacts as eye candy. Not for .pptx files or polished conference talks.
+---
+
+# HackMD deck
+
+```markdown
+---
+title: Good Fences Make Good Agents
+type: slide
+---
+
+# Good Fences Make Good Agents
+
+---
+
+## ✅ TADA: Monday's roundup drafts itself
+
+---
+
+## How: who holds what
+
+![wiring](weekly-roundup-wiring.png)
+```
+
+Example: [Good Fences Make Good Agents](../../../capsite/docs/good-fences-slides.md); an early, overboard one: [Jun 25 slides](https://hackmd.io/T9-oFWEPSb2zzqWAGFv60Q#/).
+
+## Context
+
+A talk at something like Agoric's engineering show & tell: "Presentations should take little to no preparation", by engineers for engineers. The work already exists in repos, commits, test output, and session transcripts.
+
+## Problem
+
+**A deck has to hook the room and carry a technical story in a few minutes, without hours of prep.**
+
+## Forces
+
+- The audience follows up afterward, or doesn't; the deck is no place to ask.
+- A TADA from a side thread leaves the audience waiting for a payoff that never comes.
+- Designed, built in dev, and deployed look alike on a slide.
+- Real code and real output convince; paraphrase doesn't.
+- Every slide costs attention ([grice-maxims](../grice-maxims/SKILL.md)).
+- Images in a repo don't show up in HackMD until uploaded.
+
+## Therefore
+
+**Tell it as a flashback, built from real artifacts, with emoji tags that add up to a retro.**
+
+The arc:
+
+1. TADA! Look what I did. It must be on the thread the talk follows.
+2. Now that you're hooked, how I did that.
+3. Eye candy along the way: diagrams, verbatim code, test output.
+4. Conclusions and challenges. Slides **show** challenges; they don't pose questions.
+
+Ground every slide in the record: quote code and test output verbatim (trim with `...`), check claims against the code and git history, and mark what's only designed or not deployed with ⏳.
+
+Tag slides and bullets as you go; the last slide gathers them:
+
+- wins: ✅ shipped · ✨ insight · 🙌 help, or a gift from someone else's work
+- friction and follow-ups: ⏳ delays, not yet · 🧰 fragile tooling, ceremony · 💤 silent failures · 📘 docs · 🔔 alerts · 📈 observability · 🪄 surprises · 🔧 fixes owed · 🧱 walls
+
+Write the deck in the repo the talk is about (e.g. `docs/<title>-slides.md`), images beside it, and commit it.
+
+## Resulting context
+
+The deck takes an hour, not a day, and the retro slide doubles as a to-do list. The user pastes it into HackMD and uploads the images.