fix(yaml): tighten parse() and parseAll() types

[tomas-zijdemans]

fix(yaml): tighten parse() and parseAll() types

• parseAll() is typed unknown[] to match its implementation.
• ParseOptions.onWarning is narrowed from Error to SyntaxError, matching what the loader actually dispatches.
• @throws {SyntaxError} is documented on parseAll(), and parse()'s @throws clarifies the multi-document case.

Mirrored in unstable_parse.ts. All changes are non-breaking by subtyping (unknown[] ⊆ unknown) and function-parameter contravariance ((Error) => void is assignable to (SyntaxError) => void).

[codecov]

Codecov Report

❌ Patch coverage is 57.14286% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.61%. Comparing base (a496da2) to head (165a0aa).

Files with missing lines	Patch %	Lines
yaml/unstable_parse.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7125      +/-   ##
==========================================
- Coverage   94.61%   94.61%   -0.01%     
==========================================
  Files         634      634              
  Lines       51801    51805       +4     
  Branches     9329     9329              
==========================================
+ Hits        49011    49013       +2     
- Misses       2216     2218       +2     
  Partials      574      574              

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