Fix invalid ANSI SGR escape code in JSON and diff colorization

Replace `1;38` with `1;37` (bold white) in the delimiter/header
color constant. SGR parameter 38 is the extended foreground color
prefix and requires sub-parameters (e.g. `38;5;n` or `38;2;r;g;b`),
so using it bare produces an invalid escape sequence. Most terminals
silently ignore the malformed parameter, masking the bug.

Fixes cli#12683

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: BagToad

pkg/cmd/pr/diff/diff.go

@@ -190,7 +190,7 @@ func fetchDiff(httpClient *http.Client, baseRepo ghrepo.Interface, prNumber int,
 const lineBufferSize = 4096
 
 var (
-	colorHeader   = []byte("\x1b[1;38m")
+	colorHeader   = []byte("\x1b[1;37m")
 	colorAddition = []byte("\x1b[32m")
 	colorRemoval  = []byte("\x1b[31m")
 	colorReset    = []byte("\x1b[m")

pkg/cmd/pr/diff/diff_test.go

@@ -179,7 +179,7 @@ func Test_diffRun(t *testing.T) {
 				Patch:       false,
 			},
 			wantFields: []string{"number"},
-			wantStdout: fmt.Sprintf(testDiff, "\x1b[m", "\x1b[1;38m", "\x1b[32m", "\x1b[31m"),
+			wantStdout: fmt.Sprintf(testDiff, "\x1b[m", "\x1b[1;37m", "\x1b[32m", "\x1b[31m"),
 			httpStubs: func(reg *httpmock.Registry) {
 				stubDiffRequest(reg, "application/vnd.github.v3.diff", fmt.Sprintf(testDiff, "", "", "", ""))
 			},
@@ -313,7 +313,7 @@ func Test_colorDiffLines(t *testing.T) {
 				"%[4]s+foo%[2]s\n%[5]s-b%[1]sr%[2]s\n%[3]s+++ baz%[2]s\n",
 				strings.Repeat("a", 2*lineBufferSize),
 				"\x1b[m",
-				"\x1b[1;38m",
+				"\x1b[1;37m",
 				"\x1b[32m",
 				"\x1b[31m",
 			),

pkg/jsoncolor/jsoncolor.go

@@ -9,7 +9,7 @@ import (
 )
 
 const (
-	colorDelim  = "1;38" // bright white
+	colorDelim  = "1;37" // bold white
 	colorKey    = "1;34" // bright blue
 	colorNull   = "36"   // cyan
 	colorString = "32"   // green

pkg/jsoncolor/jsoncolor_test.go

@@ -34,7 +34,7 @@ func TestWrite(t *testing.T) {
 				r:      bytes.NewBufferString(`{}`),
 				indent: "",
 			},
-			wantW:   "\x1b[1;38m{\x1b[m\x1b[1;38m}\x1b[m\n",
+			wantW:   "\x1b[1;37m{\x1b[m\x1b[1;37m}\x1b[m\n",
 			wantErr: false,
 		},
 		{
@@ -43,9 +43,9 @@ func TestWrite(t *testing.T) {
 				r:      bytes.NewBufferString(`{"hash":{"a":1,"b":2},"array":[3,4]}`),
 				indent: "\t",
 			},
-			wantW: "\x1b[1;38m{\x1b[m\n\t\x1b[1;34m\"hash\"\x1b[m\x1b[1;38m:\x1b[m " +
-				"\x1b[1;38m{\x1b[m\n\t\t\x1b[1;34m\"a\"\x1b[m\x1b[1;38m:\x1b[m 1\x1b[1;38m,\x1b[m\n\t\t\x1b[1;34m\"b\"\x1b[m\x1b[1;38m:\x1b[m 2\n\t\x1b[1;38m}\x1b[m\x1b[1;38m,\x1b[m" +
-				"\n\t\x1b[1;34m\"array\"\x1b[m\x1b[1;38m:\x1b[m \x1b[1;38m[\x1b[m\n\t\t3\x1b[1;38m,\x1b[m\n\t\t4\n\t\x1b[1;38m]\x1b[m\n\x1b[1;38m}\x1b[m\n",
+			wantW: "\x1b[1;37m{\x1b[m\n\t\x1b[1;34m\"hash\"\x1b[m\x1b[1;37m:\x1b[m " +
+				"\x1b[1;37m{\x1b[m\n\t\t\x1b[1;34m\"a\"\x1b[m\x1b[1;37m:\x1b[m 1\x1b[1;37m,\x1b[m\n\t\t\x1b[1;34m\"b\"\x1b[m\x1b[1;37m:\x1b[m 2\n\t\x1b[1;37m}\x1b[m\x1b[1;37m,\x1b[m" +
+				"\n\t\x1b[1;34m\"array\"\x1b[m\x1b[1;37m:\x1b[m \x1b[1;37m[\x1b[m\n\t\t3\x1b[1;37m,\x1b[m\n\t\t4\n\t\x1b[1;37m]\x1b[m\n\x1b[1;37m}\x1b[m\n",
 			wantErr: false,
 		},
 		{
@@ -63,7 +63,7 @@ func TestWrite(t *testing.T) {
 				r:      bytes.NewBufferString(`{{`),
 				indent: "",
 			},
-			wantW:   "\x1b[1;38m{\x1b[m\n",
+			wantW:   "\x1b[1;37m{\x1b[m\n",
 			wantErr: true,
 		},
 	}