feat(opencode): the OpenCode harness, checked against its goldens

The tool source generated from the schema, the home with its view, the
shared and per-process environments, the permission rules, the commands,
the warm-up under the supervisor, the event stream and the
classification, its patterns as hand-written scanners. The goldens record
the answer for each, a warm-up against a fake opencode included.

A timed-out supervised command now gets SIGTERM, so the supervisor takes
its tree down (SIGKILL 10 s later); any other child gets SIGKILL. :Json
gains DumpCompact.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

implementations/Crafter.Review-Mcp.cpp

@@ -33,7 +33,7 @@ namespace Crafter::Review::Mcp {
     }
 
     std::string ConfigJson(const Json& config) {
-        return config.dump(-1, ' ', true, Json::error_handler_t::replace);
+        return DumpCompact(config);
     }
 
     fs::path OutputDir(const fs::path& scratch, std::string_view label) {