refactor: convert @ts-ignore to @ts-expect-error where the error always fires

[tomas-zijdemans]

Converts 16 @ts-ignore comments across 8 files to @ts-expect-error. No runtime changes, comments only.

@ts-ignore suppresses an error whether or not it exists, so when a suppressed error gets fixed upstream, the stale comment sticks around and hides future problems. @ts-expect-error fails the build the moment the error disappears, which makes it self-cleaning. The compiler now guards these 16 spots for free.

I audited all 22 @ts-ignore comments in the repo and only converted the ones where the error is guaranteed in every configuration:

• Test files passing deliberately invalid arguments (csv, collections, crypto, text)
• testing/mock.ts: the TS2509 in constructorSpy is inherent to extending a generic constructor
• random/_test_utils.ts: typed-array mocking that can't satisfy the constructor types
• _tools/check_docs.ts: accessing .doc on the un-narrowed JsDocTag union

The remaining 8 stay as @ts-ignore on purpose. Their errors are conditional: Deno.lint only exists in Deno >= 2.2 types, the media_types comments work around dnt issue #148 (no error under Deno), time_test.ts depends on runtime lib types, and the FFI type in cli/_tools needs --unstable-ffi. Converting those would break the cross-version CI matrix.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.00%. Comparing base (ad7c87b) to head (3edcadb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7243   +/-   ##
=======================================
  Coverage   95.00%   95.00%           
=======================================
  Files         617      617           
  Lines       51674    51674           
  Branches     9326     9326           
=======================================
+ Hits        49093    49094    +1     
  Misses       2038     2038           
+ Partials      543      542    -1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.