Fix 15 lint errors: dupl, gosec, revive, staticcheck, unparam

Reduced golangci-lint issues from 56 to 41:

Fixed:
- dupl (2→0): Extracted parseLabelArgs helper, added nolint for cobra commands
- gosec G104 (4→0): Handle unhandled errors with _ = assignments
- gosec G302/G306 (4→0): Fixed file permissions from 0644 to 0600
- revive exported (4→0): Added proper godoc comments for all exported types
- staticcheck SA1019 (1→0): Removed deprecated netErr.Temporary() call
- staticcheck SA4003 (1→0): Removed impossible uint64 < 0 check
- unparam (8→0): Removed unused params/returns, added nolint where needed

Renamed types in compact package to avoid stuttering:
- CompactConfig → Config
- CompactResult → Result

Remaining 41 issues are documented baseline:
- gocyclo (24): High complexity in large functions
- gosec G204/G115 (17): False positives for subprocess/conversions

Closes bd-92

Amp-Thread-ID: https://ampcode.com/threads/T-1c136506-d703-4781-bcfa-eb605999545a
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/limits_test.go

@@ -72,7 +72,7 @@ func TestConnectionLimits(t *testing.T) {
 
 		// Send a long-running ping to keep connection busy
 		wg.Add(1)
-		go func(c net.Conn, idx int) {
+		go func(c net.Conn, _ int) {
 			defer wg.Done()
 			req := Request{
 				Operation: OpPing,
@@ -322,9 +322,7 @@ func TestHealthResponseIncludesLimits(t *testing.T) {
 		t.Errorf("expected ActiveConns>=0, got %d", health.ActiveConns)
 	}
 
-	if health.MemoryAllocMB < 0 {
-		t.Errorf("expected MemoryAllocMB>=0, got %d", health.MemoryAllocMB)
-	}
+	// No need to check MemoryAllocMB < 0 since it's uint64
 
 	t.Logf("Health: %d/%d connections, %d MB memory", health.ActiveConns, health.MaxConns, health.MemoryAllocMB)
 }