encoding/json inconsistent treatment of runes

[AntonGorov195]

Context

    Odin:    dev-2025-08:fb4641307
    OS:      Linux Mint 22.1, Linux 6.8.0-90-generic
    CPU:     Intel(R) Core(TM) i5-9400F CPU @ 2.90GHz
    RAM:     15929 MiB
    Backend: LLVM 20.1.8

Json marshal correctly handles runes, unmarshal doesn't.

package json_rune

import "core:encoding/json"
import "core:fmt"

main :: proc() {
	m := marshal_rune()
	unmarshal_rune(m)
}
marshal_rune :: proc() -> []u8 {
	val, err := json.marshal('a')
	if err != nil {
		fmt.eprintln("Error, json marshal not working with runes")
	} else {
		fmt.println("json marshal works with runes:", string(val))
	}
	return val
}
unmarshal_rune :: proc(data: []u8) {
	r: rune
	err := json.unmarshal(data, &r)
	if err != nil {
		fmt.eprintln("error, json unmarshal not working with runes")
	} else {
		fmt.println("json unmarshal works with runes:", r)
	}
}

Expected Behavior

json marshal works with runes: "a"
json unmarshal works with runes: a

or

Error, json marshal not working with runes
error, json unmarshal not working with runes

Current Behavior

json marshal works with runes: "a"
error, json unmarshal not working with runes

Steps to Reproduce

Run the sample code above with odin run .