fix: guard parseByteSize against uint64-to-int64 overflow

humanize.ParseBytes returns uint64; values above math.MaxInt64 (e.g.
"9EiB") would silently wrap to negative on the int64 cast. Now returns
a clear error instead.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sangwa

internal/config.go

@@ -3,6 +3,7 @@ package app
 import (
 	"fmt"
 	"log/slog"
+	"math"
 	"net/url"
 	"path/filepath"
 	"regexp"
@@ -336,6 +337,9 @@ func parseByteSize(s string) (int64, error) {
 	if err != nil {
 		return 0, fmt.Errorf("invalid byte size %q: %w", s, err)
 	}
+	if n > uint64(math.MaxInt64) {
+		return 0, fmt.Errorf("byte size %q overflows int64", s)
+	}
 	return int64(n), nil
 }
 

internal/endorsements_test.go

@@ -474,6 +474,7 @@ func TestParseByteSize(t *testing.T) {
 		{"abc", 0, true},
 		{"-1MiB", 0, true},
 		{"-5", 0, true},
+		{"9EiB", 0, true}, // overflows int64
 	}
 
 	for _, tt := range tests {