#43 The guide and the build page start with installing the skill

Closes #42. Stacked on #41: its base is feat/skill-zips, so merge #41 first, and this one moves to main after it.

What changes

• Guide (/h5p/create-with-ai/): step 1 is "Install the skill, once". The section #41 added below the steps moves up and gains a Grok line, so there are six steps. The seven prompts say "Use the h5p-author skill to make…" and carry no address. The lead no longer says "nothing to install". In Help, "The chat can't open the address" becomes "The chat doesn't use the skill".
• Build page: "How it works" is install, ask, play. Its prompt names the skill, and the feature card says which chats take the zip.
• Links: the footer's second guide and the home card's "For a chat" go to the guide's install step. No page links to /h5p/skill/ any more.
• /h5p/skill/ keeps answering, for installed copies of the skill and for old prompts. Only one sentence on it changes: it names Grok.
• README, and two comments in vite.config.ts, say what the bundles are for now that Grok was seen building from them.

Titles, descriptions and the home card's text are untouched: Claude, ChatGPT and Grok all take a zip.

Checked

• pnpm build passes.
• 66 checks in Chromium, at 1280 px and 390 px, on the local build:
  • the guide's six steps in order, and the build page's three;
  • each prompt names the skill and carries no address;
  • the install list and its zip links (Claude and Grok get h5p-author.zip, ChatGPT its plugin zip);
  • the top bar's Install link and the build page's link land on the install heading;
  • no link to /h5p/skill/ on any page, no sideways scroll, no console errors;
  • /h5p/skill/, its files, both zips and the bundles still answer.
• The 34 damaged-link checks from #39 still hold on this build.
• Not run: Firefox and WebKit, which are not installed here.

Grok's line rests on the owner's test of 2026-11-13: h5p-author-0.9.6.zip, the same entries as the site's h5p-author.zip, imported under Skills, then Import. Grok built the .h5p in the chat from the two downloaded files after its npx timed out.

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Summary by cubic

Closes #42. The guide and build page now start with installing the h5p-author skill, and every prompt names the skill instead of sending the chat to read /h5p/skill/.

• Step 1 of the guide is now the install, with per-chat instructions for Claude, ChatGPT, Grok, Open WebUI and terminal agents; the remaining five steps follow.
• The build page's steps are install, ask, play, and its feature card says which chats take the zip.
• No page links to /h5p/skill/ any more: the footer and home card go to the guide's install step, and the page stays for installed copies of the skill and old prompts.
• README and vite.config.ts comments now describe the bundles as what Grok built from when its npx timed out.