chore: optimize Dockerfile layers and remove unused reflect import

Dockerfile

@@ -8,15 +8,11 @@ RUN apk add --no-cache git ca-certificates
 
 WORKDIR /src
 
-# Copy *both* dependency files first so Docker-layer caching works
-COPY go.mod go.sum ./
-RUN go mod download
-
-# Bring in the rest of the source
+# Bring in the source (vendor dir included)
 COPY . .
 
-# Build static binary
-RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o /out/action ./main.go
+# Build static binary using vendored dependencies
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -mod=vendor -o /out/action ./main.go
 
 ########################
 # — Runtime stage —

main.go

@@ -7,7 +7,6 @@ import (
 	"log"
 	"os"
 	"os/exec"
-	"reflect"
 	"strconv"
 	"strings"