Fix cursor metrics in SkikoParagraph

[gavr (gavr123456789)]

Fixes CMP-8371 Text cursor shrinks after typing begins when a TextField
There are 2 problems fixed.

1. cursor height is different between empty string and non-empty string

Screen.Recording.2026-09-09.at.22.36.40.mov

2. new symbol on the second line changes the baseline when font size is larger than line height

Screen.Recording.2026-09-09.at.22.38.07.mov

(fix by SkikoParagraphBuilder.nonAndroid.kt file)

To reproduce:

 Row(
            modifier = Modifier.fillMaxWidth(),
            horizontalArrangement = Arrangement.SpaceEvenly
        ) {

            var text by remember { mutableStateOf("") }
            val textFieldStyle = LocalTextStyle.current.copy(fontSize = 64.sp)
            TextField(
                value = text,
                onValueChange = {
                    println(
                        "[TextFieldDebug] text=${it} " +
                            "length=${it.length} style=$textFieldStyle"
                    )
                    text = it
                },
                modifier = Modifier.onFocusChanged {
                    println(
                        "[TextFieldDebug] focus=" +
                            "isFocused=${it.isFocused} isCaptured=${it.isCaptured}"
                    )
                },
                textStyle = textFieldStyle,
            )

            Column(modifier = Modifier.width(340.dp)) {
                var multilineText by remember { mutableStateOf("") }
                TextField(
                    value = multilineText,
                    onValueChange = { multilineText = it },
                    label = { Text("Multiline: 48sp font / 28sp lineH") },
                    textStyle = LocalTextStyle.current.copy(fontSize = 48.sp, lineHeight = 28.sp),
                    maxLines = 4,
                    modifier = Modifier.fillMaxWidth().height(150.dp),
                )

                var monospaceText by remember { mutableStateOf("") }
                TextField(
                    value = monospaceText,
                    onValueChange = { monospaceText = it },
                    label = { Text("Monospace: 32sp font / 48sp lineH") },
                    textStyle = LocalTextStyle.current.copy(
                        fontSize = 32.sp,
                        fontFamily = FontFamily.Monospace,
                        lineHeight = 48.sp,
                    ),
                    modifier = Modifier.fillMaxWidth(),
                )

                var smallText by remember { mutableStateOf("") }
                TextField(
                    value = smallText,
                    onValueChange = { smallText = it },
                    label = { Text("Small: 14sp font / 20sp lineH") },
                    textStyle = LocalTextStyle.current.copy(fontSize = 14.sp, lineHeight = 20.sp),
                    modifier = Modifier.fillMaxWidth(),
                )
            }
        }

Testing

Screen.Recording.2026-09-09.at.22.48.18.mov

Release Notes

Fixes - Multiple Platforms

• Fixed the cursor metrics difference between empty and non-empty string
• Fixed line spacing when the line height is less than the font size.

[gavr (gavr123456789)]

test getBoundingBox_lineHeight is broken after my second fix.
https://youtrack.jetbrains.com/issue/CMP-7963

Expected Behavior
Hello and There should overlap each other

Now I see that this isn’t a bug: when the user chooses a font size > lineH, overlap is expected. Will unroll second fix.