fix(server): restore /config toJsonSafe projection

Reverts the redundant-cleanup hypothesis. The reproducer was upgraded
to exercise the actual gemini-auth bug shape — function and bigint
values under provider.options (a Schema.Any-typed declared field, not
an excess property) — and that fails /config encode without the
projection. Effect's onExcessProperty handles excess keys for free,
but Schema.Any pass-through plus encode validation doesn't, so the
toJsonSafe clone at the HTTP boundary is load-bearing for this case.

packages/opencode/src/server/routes/instance/httpapi/handlers/config.ts

@@ -13,9 +13,10 @@ export const configHandlers = HttpApiBuilder.group(InstanceHttpApi, "config", (h
     const configSvc = yield* Config.Service
 
     const get = Effect.fn("ConfigHttpApi.get")(function* () {
-      // Plugin `config` hooks may attach non-JSON-safe values (function,
-      // symbol, undefined, bigint) to the live config. Project a JSON-safe
-      // copy at the HTTP boundary so the response matches the typed schema
+      // Plugin `config` hooks may attach runtime-only values (functions,
+      // bigints, etc.) under schema-allowed fields like provider.options
+      // (Schema.Any). Project a JSON-safe copy at the HTTP boundary so
+      // response encode succeeds and clients see the typed schema shape
       // (mirrors Provider.toPublicInfo in #26550).
       return toJsonSafe(yield* configSvc.get())
     })