Add the schulcloud CLI, and document the split

The CLI talks only to the Pi's /api surface and holds no Schulcloud
credential — only the same bearer token the Claude connector uses. That
is not layering for its own sake: a Schulcloud session dies after two
hours idle and a CLI process lives for seconds, so a CLI with its own
token would be dead most times you reached for it. Routing through the
Pi means one session, one keepalive, one monthly cookie paste.

sync is a one-way mirror, which follows from the data rather than from
scope-cutting: file records are immutable upstream, so there is no
versioning, no conflict resolution and no merge. State is keyed by file
record id with the path as derived output, so an upstream rename moves
the local file instead of duplicating it — verified against the live
server. Verification is size-only because the download endpoint exposes
no ETag and Schulcloud publishes no hash; size still catches the failure
that happens, a truncated download. Downloads land on a .part neighbour
and are renamed, so an interrupted run leaves no half-file that a later
run mistakes for complete. Deletions are reported but not propagated —
a teacher removing a worksheet is no reason to destroy the student's
copy — with --prune to opt in.

what_changed now clamps to the oldest stored generation instead of
refusing, and says it did: "what's new this week" is a reasonable
question to ask a two-day-old index.

Two build bugs caught by the checks rather than by luck: the smoke
harness constructed the app without services, so the index-backed tools
were never exercised; and the Docker build could not see
scripts/copy-assets.mjs, so the image would have shipped without
migrations and silently degraded to live-only.

67 unit tests (9 needing Postgres), smoke green both ways — 34 checks
with an index, 32 without, because graceful degradation is a supported
mode and not a fallback nobody runs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

deploy/Caddyfile.snippet

@@ -13,17 +13,19 @@ mcp.example.org {
 	encode zstd gzip
 
 	# `schulcloud-mcp` is the Compose service name; Docker's embedded DNS
-	# resolves it on the shared network. No host port is published.
+	# resolves it on the shared network. No host port is published. One proxy
+	# serves both surfaces: /mcp for Claude and /api for the CLI.
 	reverse_proxy schulcloud-mcp:8080 {
 		# MCP's Streamable HTTP transport keeps a server-sent-events channel
 		# open for server-initiated messages. Without flush_interval -1 Caddy
 		# buffers those, and the connector appears to hang.
 		flush_interval -1
 
-		# Long enough for a `search` call, which walks every course.
+		# Long enough for a full re-crawl (~270 upstream requests) and for the
+		# CLI streaming large files out of the mirror.
 		transport http {
-			read_timeout 300s
-			write_timeout 300s
+			read_timeout 600s
+			write_timeout 600s
 		}
 	}