Enhance Makefile and README for improved validation and cache management

- Updated the Makefile to include a new `clean-disk` target for removing disk cache, and modified the `run-validation` target to clean the disk cache before starting.
- Enhanced the `check-review-labels` target to include additional file types in the search for temporary review labels, improving code hygiene checks.
- Refined the README.md to clarify the hardening section and improve the description of the `prefill` command.
- Removed the obsolete `test_cache/.gitkeep` file to clean up the repository.

steamcache/metrics/metrics.go

@@ -24,8 +24,6 @@ type Metrics struct {
 	TotalBytesServed  int64
 	TotalBytesSaved   int64 // bytes served from cache instead of being re-downloaded from upstream
 
-
-
 	// Cache metrics
 	MemoryCacheSize int64
 	DiskCacheSize   int64
@@ -194,8 +192,8 @@ func (m *Metrics) GetStats() *Stats {
 		RateLimited:        atomic.LoadInt64(&m.RateLimited),
 		HitRate:            hitRate,
 		AvgResponseTime:    avgResponseTime,
-		TotalBytesServed: atomic.LoadInt64(&m.TotalBytesServed),
-		TotalBytesSaved:  atomic.LoadInt64(&m.TotalBytesSaved),
+		TotalBytesServed:   atomic.LoadInt64(&m.TotalBytesServed),
+		TotalBytesSaved:    atomic.LoadInt64(&m.TotalBytesSaved),
 		MemoryCacheSize:    atomic.LoadInt64(&m.MemoryCacheSize),
 		DiskCacheSize:      atomic.LoadInt64(&m.DiskCacheSize),
 		MemoryCacheHits:    atomic.LoadInt64(&m.MemoryCacheHits),
@@ -242,18 +240,17 @@ func (m *Metrics) Reset() {
 
 // Stats represents a snapshot of metrics
 type Stats struct {
-	TotalRequests      int64
-	CacheHits          int64
-	CacheMisses        int64
-	CacheCoalesced     int64
-	Errors             int64
-	RateLimited        int64
-	HitRate            float64
-	AvgResponseTime    time.Duration
-	TotalBytesServed  int64
-	TotalBytesSaved   int64
-	MemoryCacheSize   int64
-
+	TotalRequests    int64
+	CacheHits        int64
+	CacheMisses      int64
+	CacheCoalesced   int64
+	Errors           int64
+	RateLimited      int64
+	HitRate          float64
+	AvgResponseTime  time.Duration
+	TotalBytesServed int64
+	TotalBytesSaved  int64
+	MemoryCacheSize  int64
 
 	DiskCacheSize      int64
 	MemoryCacheHits    int64