Offer courses and rooms as MCP resources, with two German prompts

A course or room can now be attached to a message rather than fetched:
schulcloud://courses/<id> and schulcloud://rooms/<id> carry exactly what
get_course and get_room return. Deliberately coarse — a picker lists every
resource at once, which suits some twenty courses and not a thousand files.

Two prompts, in German because the school is: zusammenfassung summarises a
course or room, and pruefungsvorbereitung prepares for an exam with practice
questions and a study plan. Each embeds the overview and says where material
hides and what cannot be read.

Claude Code shaped the details, read from its bundle rather than its docs.
It splits prompt arguments on whitespace and drops extra words, so words
arrive joined with "_", and courses match by fragments, whole words first,
so LF1 is not ambiguous with LF10. Its @ autocomplete shows a resource's
description, so the description carries the name. Errors are ProtocolError,
because McpError's message prefix is doubled by the client.

Verified in interactive Claude Code: @-mention, autocomplete and the prompt
commands. 157 tests. Smoke 67/67 live; 69/69 and 67/67 on the local instance.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/ROADMAP.md

@@ -98,8 +98,12 @@ Genuinely unavailable, not merely uncovered:
 
 - **Video/audio transcription** — this account has 5 MP4s and a WebM that are
   currently just "here is a file you cannot read".
-- **MCP resources and prompts** — expose courses/boards as attachable resources;
-  canned prompts such as "summarise this week's homework".
+- **MCP resources and prompts — partly built.** Courses and rooms are resources,
+  and there are two German prompts (`zusammenfassung`, `pruefungsvorbereitung`).
+  Still open: files as resources — about a thousand of them do not fit a picker
+  that lists every entry, so they need a browsing UI (an MCP App) rather than a
+  longer list — and claude.ai, which cannot reach a server on localhost and does
+  not send a static bearer token.
 - **Calendar** — a separate `schulcloud-calendar` service, not part of the v3 API
   mapped in `API.md`.