chore: add explicit types for public API

[susnux]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 4.76190% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.79%. Comparing base (4780816) to head (df04aa6).

Files with missing lines	Patch %	Lines
lib/filepicker-builder.ts	0.00%	13 Missing ⚠️
lib/dialogs.ts	12.50%	7 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2426   +/-   ##
=======================================
  Coverage   43.79%   43.79%           
=======================================
  Files          15       15           
  Lines         427      427           
  Branches       81       81           
=======================================
  Hits          187      187           
  Misses        211      211           
  Partials       29       29           

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