feat(internal/librarian/java): add whitespace formatting helpers for README rendering

internal/librarian/java/readme.go

@@ -167,6 +167,45 @@ func extractTitle(filePath string) (string, error) {
 	return title, nil
 }
 
+// minLeadingSpaces finds the minimum number of leading spaces across non-empty lines.
+func minLeadingSpaces(lines []string) int {
+	if len(lines) == 0 {
+		return 0
+	}
+	minSpaces := -1
+	for _, line := range lines {
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
+		spaces := len(line) - len(strings.TrimLeft(line, " "))
+		if minSpaces == -1 || spaces < minSpaces {
+			minSpaces = spaces
+		}
+	}
+	if minSpaces == -1 {
+		return 0
+	}
+	return minSpaces
+}
+
+// trimLeadingWhitespace computes minimum leading space indentation and trims it.
+func trimLeadingWhitespace(lines []string) string {
+	if len(lines) == 0 {
+		return ""
+	}
+	minSpaces := minLeadingSpaces(lines)
+	var sb strings.Builder
+	for _, line := range lines {
+		if strings.TrimSpace(line) == "" {
+			sb.WriteString("\n")
+			continue
+		}
+		sb.WriteString(line[minSpaces:])
+		sb.WriteString("\n")
+	}
+	return sb.String()
+}
+
 // collectSnippetFiles recursively scans dir/samples for Java and XML files containing snippets.
 func collectSnippetFiles(dir string) ([]string, error) {
 	samplesDir := filepath.Join(dir, "samples")

internal/librarian/java/readme_test.go

@@ -478,6 +478,73 @@ func TestExtractTitle_Error(t *testing.T) {
 	}
 }
 
+func TestMinLeadingSpaces(t *testing.T) {
+	for _, test := range []struct {
+		name  string
+		lines []string
+		want  int
+	}{
+		{
+			name:  "two lines indented",
+			lines: []string{"  foo", "    bar"},
+			want:  2,
+		},
+		{
+			name:  "zero indented line",
+			lines: []string{"foo", "  bar"},
+			want:  0,
+		},
+		{
+			name:  "empty slice",
+			lines: nil,
+			want:  0,
+		},
+		{
+			name:  "only whitespace lines",
+			lines: []string{"   ", "\t"},
+			want:  0,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			got := minLeadingSpaces(test.lines)
+			if diff := cmp.Diff(test.want, got); diff != "" {
+				t.Errorf("mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func TestTrimLeadingWhitespace(t *testing.T) {
+	for _, test := range []struct {
+		name  string
+		lines []string
+		want  string
+	}{
+		{
+			name:  "standard indentation",
+			lines: []string{"  int x = 1;", "    int y = 2;"},
+			want:  "int x = 1;\n  int y = 2;\n",
+		},
+		{
+			name:  "with blank line",
+			lines: []string{"  int x = 1;", "", "  int y = 2;"},
+			want:  "int x = 1;\n\nint y = 2;\n",
+		},
+		{
+			name:  "empty input",
+			lines: nil,
+			want:  "",
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			got := trimLeadingWhitespace(test.lines)
+			if diff := cmp.Diff(test.want, got); diff != "" {
+				t.Errorf("mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
 func TestCollectSnippetFiles(t *testing.T) {
 	for _, test := range []struct {
 		name       string