Config parse errors echo the substituted text, not the file as written

Description

Hit this while fixing a typo in my opencode.json.

I had a syntax error (forgot the value after "model":) and the config uses
{env:DEMO_KEY} for the API key. The error under "--- JSONC Input ---" printed
my config back with the actual key value where {env:DEMO_KEY} was.

I'd expect it to quote the file the way I wrote it. tui.json goes through the
same path, and that one ends up in ~/.local/share/opencode/log/opencode.log.

Plugins

No response

OpenCode version

1.18.18

Steps to reproduce

1. Put this in opencode.json:
   {
   "$schema": "https://opencode.ai/config.json",
   "provider": { "anthropic": { "options": { "apiKey": "{env:DEMO_KEY}" } } },
   "model":
   }
2. DEMO_KEY=sk-live-DO-NOT-PRINT opencode run "hi"
3. Look at the block under "--- JSONC Input ---" - the apiKey line shows
   sk-live-DO-NOT-PRINT instead of {env:DEMO_KEY}, and the reported line
   number doesn't match the file.

Screenshot and/or share link

Operating System

macOS 26.0.1

Terminal

No response