Update chokidar

[andriyor]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything or linked relevant results below
• I made sure the docs are up to date
• I included tests (or that’s not needed)

Description of changes

Bumps chokidar from ^3.0.0 to ^5.0.0. Types needed two tweaks: FSWatcher
is imported as a type (it is no longer a namespace), and done is cast because
error now passes unknown. Dropped glob support does not affect us —
fileSet.origins are resolved paths. Existing --watch tests cover it.

Likely a major, though: chokidar@5 wants Node >= 20.19.0 while the readme
promises Node 16 for this line, and #19 was labelled semver/major for the same
reason. I left the readme and engines alone since dropping Node 16 is your
call. Happy to hold this for the next major.

Second commit fixes four pre-existing type errors in lib/parse-argv.js under
TypeScript 5.9.3 (floating typescript: ^5.0.0); main is red without it, so
this PR could not go green. Glad to split it out if you prefer.

[andriyor]

CI was red on the type-check, but those four lib/parse-argv.js errors are pre-existing on main and unrelated to chokidar — I reproduced them on a clean clone of main with TypeScript 5.9.3 (the project floats typescript: ^5.0.0).

TS 5.9 reports conditional-return mismatches on the ternary branches rather than on the return, so the @ts-expect-error in toArray no longer covers them, and lastIfArray was relying on a check that has since tightened.

Pushed be75301 as a separate commit to unblock this PR. Happy to split it into its own PR if you'd rather keep this one to just the chokidar bump.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2850f77) to head (061e6c3).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #34   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            4         4           
  Lines          906       908    +2     
=========================================
+ Hits           906       908    +2     

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