OpenCode substitutes {env:VAR} and {file:path} in config text at load
time, but OMP's OpenCode discovery ran the generic ${VAR}-only
expandEnvVarsDeep, leaving those tokens literal. An MCP header like
`Bearer {env:MCP_KEY}` reached the server verbatim and returned 401.
The OpenCode loader now applies OpenCode's own substitution to raw
config text before parsing: {env:VAR} -> env value or empty string,
{file:path} -> trimmed, JSON-escaped file contents resolved relative to
the config dir / ~ / absolute, skipping tokens on // comment lines.
Fixes#8778
roboomp
1441fdb28b