chore: remove Ruby implementation and tooling

docker/behavior/Dockerfile

@@ -1,13 +1,21 @@
+FROM golang:1.26-alpine AS builder
+
+WORKDIR /workspace
+COPY go.mod go.sum /workspace/
+RUN go mod download
+COPY . /workspace
+RUN mkdir -p /workspace/dist && \
+    go build -o /workspace/dist/homesick-go ./cmd/homesick
+
 FROM alpine:3.21
 
 RUN apk add --no-cache \
     bash \
     ca-certificates \
-    git \
-    ruby \
-    ruby-thor
+    git
 
 WORKDIR /workspace
 COPY . /workspace
+COPY --from=builder /workspace/dist/homesick-go /workspace/dist/homesick-go
 
 ENTRYPOINT ["/workspace/test/behavior/behavior_suite.sh"]