Rewrite in Go: static binaries, zero runtime dependencies

Replace Node.js + Python codebase with three Go binaries:
- claude-statusline: CLI status bar for Claude Code
- claude-fetcher: standalone cron job for API usage
- claude-widget: system tray icon (fyne-io/systray + fogleman/gg)

All CGO-free for trivial cross-compilation. Add nfpm .deb packaging
with autostart and cron. CI pipeline produces Linux + Windows binaries,
.deb, .tar.gz, and .zip release assets.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/statusline/main.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+
+	"git.davoryn.de/calic/claude-statusline/internal/fetcher"
+)
+
+const (
+	filledBlock = "\u2593"
+	lightBlock  = "\u2591"
+)
+
+// stdinData is the JSON structure from Claude Code's stdin.
+type stdinData struct {
+	ContextWindow struct {
+		UsedPercentage float64 `json:"used_percentage"`
+	} `json:"context_window"`
+}
+
+func bar(pct float64, width int) string {
+	pct = math.Max(0, math.Min(100, pct))
+	filled := int(math.Floor(pct / (100.0 / float64(width))))
+	return strings.Repeat(filledBlock, filled) + strings.Repeat(lightBlock, width-filled)
+}
+
+func getContextPart(data *stdinData) string {
+	if data == nil {
+		return ""
+	}
+	pct := data.ContextWindow.UsedPercentage
+	return fmt.Sprintf("Context %s %d%%", bar(pct, 10), int(pct))
+}
+
+func formatMinutes(isoStr string) string {
+	if isoStr == "" {
+		return ""
+	}
+	t, err := time.Parse(time.RFC3339, isoStr)
+	if err != nil {
+		return ""
+	}
+	mins := int(math.Max(0, time.Until(t).Minutes()))
+	return fmt.Sprintf("%dM", mins)
+}
+
+func getUsagePart(data *fetcher.CacheData) string {
+	if data == nil {
+		return ""
+	}
+	if data.Error != "" {
+		switch data.Error {
+		case "auth_expired":
+			return "Token: session expired"
+		case "no_session_key":
+			return ""
+		default:
+			return "Token: error"
+		}
+	}
+
+	var parts []string
+
+	if data.FiveHour != nil && data.FiveHour.Utilization > 0 {
+		pct := data.FiveHour.Utilization
+		s := fmt.Sprintf("Token %s %d%%", bar(pct, 10), int(math.Round(pct)))
+		if mins := formatMinutes(data.FiveHour.ResetsAt); mins != "" {
+			s += " " + mins
+		}
+		parts = append(parts, s)
+	}
+
+	if data.SevenDay != nil && data.SevenDay.Utilization > 20 {
+		parts = append(parts, fmt.Sprintf("7d %d%%", int(math.Round(data.SevenDay.Utilization))))
+	}
+
+	return strings.Join(parts, " | ")
+}
+
+func main() {
+	// Read stdin (context window data from Claude Code)
+	var input stdinData
+	var hasInput bool
+	dec := json.NewDecoder(os.Stdin)
+	if err := dec.Decode(&input); err == nil {
+		hasInput = true
+	}
+
+	// Read cache
+	maxAge := 900 * time.Second
+	if v := os.Getenv("CLAUDE_USAGE_MAX_AGE"); v != "" {
+		if secs, err := strconv.Atoi(v); err == nil {
+			maxAge = time.Duration(secs) * time.Second
+		}
+	}
+	cache := fetcher.ReadCacheIfFresh(maxAge)
+
+	// Build output
+	var parts []string
+
+	if hasInput {
+		if ctx := getContextPart(&input); ctx != "" {
+			parts = append(parts, ctx)
+		}
+	}
+
+	if usage := getUsagePart(cache); usage != "" {
+		parts = append(parts, usage)
+	}
+
+	if len(parts) > 0 {
+		fmt.Println(strings.Join(parts, " | "))
+	}
+}