Use CodeMirror editor

Makefile

@@ -4,7 +4,10 @@ COMPANION_WIN := companion/datascape-companion-windows-amd64.exe
 COMPANION_LIN := companion/datascape-companion-linux-amd64
 COMPANION_SRCS := $(wildcard cmd/companion/*.go) $(wildcard cmd/companion/*.html) go.mod go.sum
 
-.PHONY: deploy companion companion-windows companion-linux companion-release
+EDITOR_BUNDLE := assets/editor/vendor/codemirror.bundle.js
+EDITOR_SRCS := $(wildcard editor-build/*.js) editor-build/package.json editor-build/package-lock.json
+
+.PHONY: deploy companion companion-windows companion-linux companion-release editor
 
 # Cross-compiled companion artifacts the wiki binary embeds. Both must exist
 # before `go build .` so embed.FS picks them up.
@@ -24,6 +27,15 @@ companion:
 	mkdir -p bin
 	go build -o bin/ ./cmd/companion
 
+# Regenerate the vendored CodeMirror bundle. One-time/dev-only step: run after
+# upgrading the @codemirror/* versions in editor-build/package.json. The built
+# artifact ($(EDITOR_BUNDLE)) is committed; `go build` only consumes it and
+# never runs Node.
+editor: $(EDITOR_BUNDLE)
+
+$(EDITOR_BUNDLE): $(EDITOR_SRCS)
+	cd editor-build && npm ci && npm run build
+
 deploy: companion-release
 	GOOS=linux GOARCH=arm GOARM=7 go build -o datascape-arm .
 	ssh $(NAS) 'kill $$(cat /share/homes/luxick/.local/bin/datascape.pid) 2>/dev/null; rm -f /share/homes/luxick/.local/bin/datascape.pid'