Add skool/classroom domain skill

domain-skills/skool/classroom.md

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+# Skool Classroom — reading and editing course/lesson content
+
+Skool communities (`skool.com/<group>`) have a Classroom of courses; each course contains
+modules (lessons). As a group admin you can read and write every lesson programmatically —
+no editor UI automation needed.
+
+## URL patterns
+
+- Classroom index: `/{group}/classroom`
+- Course page: `/{group}/classroom/{courseName}` where `courseName` is an 8-hex slug
+  (`metadata` calls it `name`; the long hex `id` is a different field).
+- A specific lesson: `?md={moduleId}` (the long 32-hex module id).
+- Edit mode: `&e=1`.
+
+## Reading course data (Next.js)
+
+Everything is in `__NEXT_DATA__` / the `/_next/data/` endpoint:
+
+- Classroom index page props: `pageProps.allCourses` — every course's `{id, name, metadata}`.
+- Course tree: `pageProps.course` = `{course, children: [{course, children}, ...]}`.
+  Course unit `unitType` is `course` | `module` (Skool calls lessons "modules"; `set` exists
+  for sections in bigger classrooms).
+- Data endpoint: `/_next/data/{buildId}/{group}/classroom/{courseName}.json?md={moduleId}&group={group}&course={courseName}`
+  with cookies. Grab `buildId` from any captured `/_next/data/` request or `__NEXT_DATA__`.
+- **Redirect trap:** without `md=`, the JSON comes back as
+  `{"pageProps":{"__N_REDIRECT":"/{group}/classroom/{name}?md=<firstModuleId>"}}` — parse the
+  `md` out of it and refetch.
+- **Lazy-desc trap:** the course tree only hydrates `metadata.desc` for the module selected
+  by `md=`. All other modules show `desc: ""` even when they have content. To dump a whole
+  course you must fetch once per module id.
+
+## Lesson content format
+
+`metadata.desc` is `"[v2]" + JSON.stringify(tiptapNodes)` — a TipTap/ProseMirror node array
+(no wrapping `{type:"doc"}`; the array is the document).
+
+Supported by the editor toolbar (and confirmed rendering): `heading` (attrs.level 1–4),
+`paragraph`, `bulletList`/`orderedList` (+`listItem` containing `paragraph`), `blockquote`
+(renders as a styled callout), `codeBlock` (`attrs:{language:null}` is fine),
+`horizontalRule`, `hardBreak`; marks: `bold`, `italic`, `strike`, `code`, and
+`link` (`attrs:{href, target:"_blank", rel:"noopener noreferrer nofollow", class:null}`).
+Content written this way round-trips cleanly through Skool's own editor.
+
+**Trap:** pasting markdown into the Skool editor stores it as literal text — `# `, `- `,
+`**bold**` all show verbatim to members, often as one `paragraph` full of `hardBreak`s.
+To fix, split paragraph content on `hardBreak`, parse the markdown yourself, and write real
+nodes back.
+
+## Writing a lesson
+
+```text
+PUT https://api2.skool.com/courses/{moduleId}
+content-type: application/json  (cookie auth — do it via in-page fetch with credentials:'include')
+{"title": "...", "desc": "[v2][...]", "transcript": null, "video_id": ""}
+```
+
+- This is exactly what the editor's SAVE sends. It does NOT touch `metadata.resources`
+  (attached files/links survive).
+- **Preserve `video_id`** — if the lesson has a video attached, send its existing id, not `""`.
+  (Check `metadata.videoLink` before writing.)
+- The server re-serializes `desc` with its own JSON key order, so verify writes by parsing
+  and comparing structurally, not by string equality.
+
+## Waits
+
+- Lesson body is client-rendered after hydration; large descs (≥15 KB) can take 10–30 s to
+  appear on a long-lived automation tab while the title + Resources render immediately.
+  Poll `document.body.innerText` for a known phrase before concluding a lesson is broken.