TypeScript: Enable strict mode incrementally

[evans-sam]

Problem

tsconfig.json does not set strict: true (nor any of its constituent flags). Effects:

• 90 explicit any usages across 8 files.
• No null-safety guarantees.
• noImplicitAny, strictNullChecks, noUncheckedIndexedAccess all off.

Why it matters

A type-system-heavy library that doesn't use its type system is shipping weaker guarantees than its users assume from the .d.ts files. Every any is a type-safety hole, and the biggest offenders (wsdl/index.ts: 23, wsdl/elements.ts: 21, client.ts: 17) are exactly the modules handling untrusted input.

Proposed approach

Enable flags incrementally, one PR each, to keep reviews manageable:

1. noImplicitAny — forces every any to be explicit.
2. strictNullChecks — likely the biggest PR; exposes all the missing | null and | undefined.
3. strictFunctionTypes + alwaysStrict — usually small.
4. noUncheckedIndexedAccess — may require careful review of array indexing.
5. Flip to strict: true and delete the individual flags.

Between each step, run npm run build && npm test. Don't add @ts-expect-error or // @ts-ignore — prefer real type fixes.

Acceptance criteria

• tsconfig.json has strict: true (or equivalent set of flags).
• any count visibly reduced (target: <30).
• No new @ts-ignore / @ts-expect-error suppressions added.
• Build and tests pass.