fix: remove --test-concurrency from test:coverage to stabilize CI

Coverage runs are CPU-bound; forcing 32 concurrent processes on a 4-CPU
CI runner causes timer contention in runtime-monitor tests, dropping
line coverage below the 95% gate. Plain tests keep --test-concurrency=32
because they are I/O-bound (sleeping in setTimeout).

Author: sharon77242

packages/agent/package.json

@@ -40,7 +40,7 @@
     "format:check": "prettier --check .",
     "test": "node --test --test-concurrency=32 --experimental-strip-types tests/**/*.test.ts tests/*.test.ts",
     "test:watch": "node --test --test-concurrency=32 --experimental-strip-types --watch tests/**/*.test.ts tests/*.test.ts",
-    "test:coverage": "node --test --test-concurrency=32 --experimental-test-coverage --test-coverage-lines=95 --test-coverage-functions=90 --test-coverage-branches=90 --experimental-strip-types tests/**/*.test.ts tests/*.test.ts",
+    "test:coverage": "node --test --experimental-test-coverage --test-coverage-lines=95 --test-coverage-functions=90 --test-coverage-branches=90 --experimental-strip-types tests/**/*.test.ts tests/*.test.ts",
     "validate": "pnpm run typecheck && pnpm run lint && pnpm run format:check && pnpm run test:coverage",
     "prepublishOnly": "node -e \"require('fs').copyFileSync('../../README.md','./README.md')\" && pnpm run build",
     "postpublish": "node -e \"require('fs').unlinkSync('./README.md')\""