export: stop an unanchored exclude from eating a plugin

The publication rsync excluded 'tools' to keep the repo-root tools/ dir
off GitHub. rsync patterns without a leading slash match at any depth, so
naming a plugin 'tools' meant plugins/tools/ was dropped too. It was
committed, exported, bundled and deployed, and the first sign of trouble
was `plugin install tools` on the server failing on a manifest.json that
had never been shipped.

The root-intended excludes are anchored, and the sync now verifies that
every plugins/*/manifest.json in the working tree came out the other side.
A silent omission of a whole plugin should not be something a deploy
discovers for us.

tools/export-github.sh

@@ -50,9 +50,9 @@ done
 rsync -a --delete \
   --exclude '.git' \
   --exclude '.gitea' \
-  --exclude 'docs' \
-  --exclude 'tools' \
-  --exclude 'mcp' \
+  --exclude '/docs' \
+  --exclude '/tools' \
+  --exclude '/mcp' \
   --exclude 'start-api.sh' \
   --exclude 'start-ui.sh' \
   --exclude 'CLAUDE.md' \
@@ -69,7 +69,7 @@ rsync -a --delete \
   --exclude 'frontend/dist*' \
   --exclude 'frontend/src/.plugins-staged' \
   --exclude 'frontend/src/router/routes.gen.js' \
-  --exclude 'instance' \
+  --exclude '/instance' \
   --exclude '.env' \
   --exclude '__pycache__' \
   --exclude '.pytest_cache' \
@@ -80,6 +80,26 @@ rsync -a --delete \
   --exclude 'scripts/site_imports/wjf/idmap.json' \
   "$WORK/" "$PUB/"
 
+# --- 1b. every bundled plugin must have survived the sync ---
+#
+# The excludes above are rsync patterns, and a pattern with no leading slash
+# matches at ANY depth. 'tools' was meant to drop the repo-root tools/ dir (this
+# script lives in it) and silently dropped plugins/tools/ as well, so a plugin
+# was committed, exported, bundled and deployed without ever being in the
+# payload - the failure only surfaced as a missing manifest.json on the server.
+# The excludes are anchored now; this check is what makes a recurrence loud.
+missing=""
+for manifest in "$WORK"/plugins/*/manifest.json; do
+  [ -e "$manifest" ] || continue
+  plugin=$(basename "$(dirname "$manifest")")
+  [ -f "$PUB/plugins/$plugin/manifest.json" ] || missing="$missing $plugin"
+done
+if [ -n "$missing" ]; then
+  echo "ERROR: bundled plugin(s) missing from the publication tree:$missing" >&2
+  echo "       an rsync --exclude above is matching them; anchor it with a leading slash." >&2
+  exit 1
+fi
+
 cd "$PUB"
 
 # --- 2. re-apply the publication wording (idempotent) ---