Section 6.1 (linter security rules) still recommends TSLint — refresh?

Section 6.1 / `sections/security/lintrules.md` currently recommends `tslint-config-security`, but TSLint was deprecated in 2019 and that package is unmaintained. The `eslint-plugin-security` link also points to the archived `nodesecurity` org instead of its current `eslint-community` home.

Section 3.2 has a couple of link bugs too: the text `eslint-plugin-node-security` links to `eslint-plugin-security`, `eslint-plugin-node` is deprecated in favor of `eslint-plugin-n`, there's a stray `/` in `/eslint-plugin-jest`, and `eslint-plugin-require` doesn't exist on npm.

I'd like to open a small English-only PR that fixes the stale links, notes the TSLint deprecation, and adds one sentence mentioning newer flat-config security plugins alongside eslint-plugin-security. Disclosure: I maintain some of those newer plugins, so I'd rather get a maintainer's nod on the framing first. Happy to keep it to pure link fixes if you prefer — the corrections stand on their own either way.

Open sections/security/lintrules.md and inspect Section 6.1 first, then locate Section 3.2 for the additional link corrections. Compare each referenced package and repository link with its current destination, and finish when the TSLint deprecation, valid links, and the agreed flat-config security-plugin wording are reflected without expanding beyond the approved English-only scope.

Written by the indexing model from the issue text.