npm config set persists invalid values but silently ignores them at runtime

npm config set accepts and persists invalid values, but later silently ignores them.

Reproduction:

node bin/npm-cli.js config set registry=not-a-url
node bin/npm-cli.js config set fetch-retries=abc
node bin/npm-cli.js config set fetch-timeout=-1

Observed behavior:

• Invalid values are written to ~/.npmrc
• npm prints warnings but exits successfully
• At runtime, npm silently omits the invalid config:
  "npm warn config omitting invalid config values"

This leaves users in a confusing state:

• Config appears set
• npm later ignores it without failing
• No clear remediation path

Expected behavior (one of):

• Reject invalid values and do not persist
• Fail with non-zero exit
• Explicitly remove invalid entries
• Require validation before writing to .npmrc

Current behavior silently corrupts config state and makes debugging difficult.

Start with the reproduction commands through node bin/npm-cli.js and inspect how config set writes invalid values to ~/.npmrc versus how runtime validation omits them. Confirm the behavior for registry, fetch-retries, and fetch-timeout; done means an agreed validation or failure behavior prevents the confusing persisted-and-ignored state.