base: add deno task npm-clean.

Author: dajiaji

CONTRIBUTING.md

@@ -117,6 +117,13 @@ allowing them to reference each other during development and testing.
 The `deno task npm-pack` command runs `npm pack --dry-run` for all packages to
 validate their structure and contents without actually creating package files.
 
+- `deno task npm-clean`: Clean npm build artifacts
+
+The `deno task npm-clean` command removes all directories and files generated by
+the `npm-build` process, returning the npm workspace to its initial state. This
+includes removing the `npm/packages`, `npm/samples`, and `npm/test` directories
+that contain the built npm packages and related files.
+
 - `deno task bun-link`: Link packages for Bun runtime testing
 
 The `deno task bun-link` command creates Bun links for all packages, enabling

deno.json

@@ -130,6 +130,7 @@
     "check:hpke-js": "cd packages/hpke-js && deno task check",
     "check:ml-kem": "cd packages/ml-kem && deno task check",
     "npm": "deno task npm-build && deno task npm-link && deno task npm-pack && cd npm && npm install",
+    "npm-clean": "rm -rf npm/packages npm/samples npm/test",
     "npm-build": "deno task npm-build:common && deno task npm-build:core && deno task npm-build:chacha20poly1305 && deno task npm-build:dhkem-x25519 && deno task npm-build:dhkem-x448 && deno task npm-build:dhkem-secp256k1 && deno task npm-build:hybridkem-x-wing && deno task npm-build:hpke-js && deno task npm-build:ml-kem",
     "npm-build:common": "cd packages/common && deno task npm-build",
     "npm-build:core": "cd packages/core && deno task npm-build",