chore(deps): replace dependency @tsconfig/node18 with @tsconfig/node20

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
@tsconfig/node18 (source) → @tsconfig/node20		replacement	18 → 20
@tsconfig/node18 (source) → @tsconfig/node20	devDependencies	replacement	18.2.6 → 20.1.0

⚠️ Renovate's replacement functionality does not currently wire in the release age for a package, so the Minimum Release Age checks can apply. You will need to manually validate the Minimum Release Age for these package(s).

This is a special PR that replaces @tsconfig/node18 with the community suggested minimal stable replacement version.

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[JP-Ellis]

@copilot Help fix any issues with this upgrade.

While doing so, make sure that:

1. Any overrides to the tsconfig do not override the (minimal) settings in the upstream config, that is:

   {
     "$schema": "https://www.schemastore.org/tsconfig",
     "display": "Node 20",
     "_version": "20.1.0",
   
     "compilerOptions": {
       "lib": ["es2023"],
       "module": "nodenext",
       "target": "es2022",
   
       "strict": true,
       "esModuleInterop": true,
       "skipLibCheck": true,
       "moduleResolution": "node16"
     }
   }

   That does mean removing some of the current options that might conflict/contradict (and if they are the same, remove them to avoid ambiguity as to the source of truth).

2. Update other config entries to ensure that we have strict type safety checks/validations enforced, and resolve any issues that arise from these checks/validations.

[Copilot]

@JP-Ellis I've opened a new pull request, #815, to work on those changes. Once the pull request is ready, I'll request review from you.

[renovate]

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