feat(service): expose build version on GET / mirroring /health

Extract a buildVersionInfo helper from HandleHealth so both endpoints
emit identical version + VCS metadata. JSON callers hitting / now get
the same release context they get from /health; under go run/test
where debug.ReadBuildInfo lacks VCS settings, version falls back to
"0.0.1" and the vcs_* keys are omitted (instead of empty strings).

The HTML branch of / is unchanged — the embedded index.html keeps its
own version-display story.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pkg/service/handlers/handlers_health.go

@@ -7,45 +7,53 @@ import (
 	"time"
 )
 
-// HandleHealth returns the health status of the service.
-func (s *Server) HandleHealth(w http.ResponseWriter, _ *http.Request) {
-	version := "0.0.1"
-	vcsRevision := ""
-	vcsTime := ""
-	vcsModified := ""
+// buildVersionInfo extracts module version + VCS metadata from the
+// runtime/debug build info, falling back to "0.0.1" when the binary
+// wasn't built with module info (e.g. local `go run`). Shared between
+// HandleHealth and HandleRoot so both endpoints report identical
+// release context; keys present-when-non-empty so a `go run` response
+// stays minimal instead of carrying empty strings.
+func buildVersionInfo() map[string]string {
+	info := map[string]string{"version": "0.0.1"}
 
-	if info, ok := debug.ReadBuildInfo(); ok {
-		if info.Main.Version != "" && info.Main.Version != "(devel)" {
-			version = info.Main.Version
-		}
+	build, ok := debug.ReadBuildInfo()
+	if !ok {
+		return info
+	}
 
-		for _, setting := range info.Settings {
-			switch setting.Key {
-			case "vcs.revision":
-				vcsRevision = setting.Value
-			case "vcs.time":
-				vcsTime = setting.Value
-			case "vcs.modified":
-				vcsModified = setting.Value
+	if build.Main.Version != "" && build.Main.Version != "(devel)" {
+		info["version"] = build.Main.Version
+	}
+
+	for _, setting := range build.Settings {
+		switch setting.Key {
+		case "vcs.revision":
+			if setting.Value != "" {
+				info["vcs_revision"] = setting.Value
+			}
+		case "vcs.time":
+			if setting.Value != "" {
+				info["vcs_time"] = setting.Value
+			}
+		case "vcs.modified":
+			if setting.Value != "" {
+				info["vcs_modified"] = setting.Value
 			}
 		}
 	}
 
+	return info
+}
+
+// HandleHealth returns the health status of the service.
+func (s *Server) HandleHealth(w http.ResponseWriter, _ *http.Request) {
 	status := map[string]interface{}{
 		"status":    "up",
 		"timestamp": time.Now().Format(time.RFC3339),
-		"version":   version,
-	}
-	if vcsRevision != "" {
-		status["vcs_revision"] = vcsRevision
 	}
 
-	if vcsTime != "" {
-		status["vcs_time"] = vcsTime
-	}
-
-	if vcsModified != "" {
-		status["vcs_modified"] = vcsModified
+	for k, v := range buildVersionInfo() {
+		status[k] = v
 	}
 
 	w.Header().Set("Content-Type", "application/json")

pkg/service/handlers/handlers_media.go

@@ -2,7 +2,7 @@ package handlers
 
 import (
 	"embed"
-	"fmt"
+	"encoding/json"
 	"io/fs"
 	"net/http"
 	"strings"
@@ -36,8 +36,25 @@ var swUpdateXML []byte
 func (s *Server) HandleRoot(w http.ResponseWriter, r *http.Request) {
 	accept := r.Header.Get("Accept")
 	if !strings.Contains(accept, "text/html") && (strings.Contains(accept, "application/json") || accept == "*/*" || accept == "") {
+		// Mirror the version + VCS metadata exposed by /health so any
+		// caller hitting "/" gets identical release context. Keys that
+		// would carry empty strings are omitted by buildVersionInfo.
+		payload := map[string]string{
+			"Bose":    "AfterTouch",
+			"service": "Go/Chi",
+			"docs":    "https://gesellix.github.io/Bose-SoundTouch/",
+		}
+
+		for k, v := range buildVersionInfo() {
+			payload[k] = v
+		}
+
 		w.Header().Set("Content-Type", "application/json")
-		_, _ = fmt.Fprintf(w, `{"Bose": "AfterTouch", "service": "Go/Chi", "docs": "https://gesellix.github.io/Bose-SoundTouch/"}`)
+
+		if err := json.NewEncoder(w).Encode(payload); err != nil {
+			http.Error(w, "Failed to encode response", http.StatusInternalServerError)
+			return
+		}
 
 		return
 	}

pkg/service/handlers/handlers_media_test.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"encoding/json"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -66,10 +67,26 @@ func TestRootEndpointJSON(t *testing.T) {
 		t.Errorf("Expected application/json content type, got %s", contentType)
 	}
 
-	body, _ := io.ReadAll(res.Body)
-	expected := `{"Bose": "AfterTouch", "service": "Go/Chi", "docs": "https://gesellix.github.io/Bose-SoundTouch/"}`
-	if strings.TrimSpace(string(body)) != expected {
-		t.Errorf("Expected body %s, got %s", expected, string(body))
+	var got map[string]string
+	if err := json.NewDecoder(res.Body).Decode(&got); err != nil {
+		t.Fatalf("failed to decode root response: %v", err)
+	}
+
+	for _, want := range []struct{ key, value string }{
+		{"Bose", "AfterTouch"},
+		{"service", "Go/Chi"},
+		{"docs", "https://gesellix.github.io/Bose-SoundTouch/"},
+	} {
+		if got[want.key] != want.value {
+			t.Errorf("payload[%q] = %q, want %q", want.key, got[want.key], want.value)
+		}
+	}
+
+	// Version mirrors /health — falls back to "0.0.1" under `go test`
+	// (debug.ReadBuildInfo reports Main.Version="(devel)") but must
+	// always be present so monitoring tools can pin a release.
+	if got["version"] == "" {
+		t.Error("expected version field to be present")
 	}
 }