core: remove @effect/language-service plugin and optimize hot path type performance

- Removed @effect/language-service from both packages/core and packages/opencode tsconfig files and dependencies

- Wrapped mergeDeep calls in config loading and LLM streaming to avoid expensive remeda conditional merge type instantiations in hot paths

- Narrowed Drizzle migrate() overload signature to avoid expensive variance checks during database initialization

These changes reduce TypeScript type-checking overhead and improve startup and runtime performance for config loading, LLM streaming, and database migrations.

packages/opencode/package.json

@@ -6,7 +6,6 @@
   "license": "MIT",
   "private": true,
   "scripts": {
-    "prepare": "effect-language-service patch || true",
     "typecheck": "tsgo --noEmit",
     "test": "bun test --timeout 30000",
     "test:ci": "mkdir -p .artifacts/unit && bun test --timeout 30000 --reporter=junit --reporter-outfile=.artifacts/unit/junit.xml",
@@ -42,7 +41,6 @@
   },
   "devDependencies": {
     "@babel/core": "7.28.4",
-    "@effect/language-service": "0.84.2",
     "@octokit/webhooks-types": "7.6.1",
     "@opencode-ai/script": "workspace:*",
     "@opencode-ai/core": "workspace:*",