Run tests against a throwaway MariaDB Docker container

- Add scripts/test.ts: starts a temporary MariaDB container on a random
  localhost port, waits for TCP readiness, runs all test files, and
  always removes the container (including on Ctrl+C)
- `bun run test` uses the script; `bun run test:unit` runs without a DB
- BUN_MARIADB_TEST_IMAGE selects the image; an existing
  BUN_MARIADB_TEST_DB skips Docker
- Document in README

Co-Authored-By: Claude Opus 5.5 <[email protected]>

package.json

@@ -29,7 +29,8 @@
         "dev": "tsc --watch",
         "compile": "rm -rf dist tsconfig.tsbuildinfo && tsc -p tsconfig.json && chmod +x dist/commands/index.js",
         "typecheck": "tsc -p tsconfig.json --noEmit",
-        "test": "bun test tests",
+        "test": "bun run scripts/test.ts",
+        "test:unit": "bun test",
         "prepublishOnly": "bun run compile"
     },
     "devDependencies": {