fix(type-plus): rename Seperator type parameter to Separator

[unional]

Summary

Renames the misspelled Seperator type parameter of StringSplit (src/string/string.ts) and StringPlus.Split (src/string/string_plus.ts) to Separator, and fixes the website string docs to match. No Seperator or seperator is left in the repo. That includes llms.txt and src/string/readme.md.

Not breaking, because type parameter names are not part of the call contract. Patch changeset.

Verification

• pnpm verify passes

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: eae3b19

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
type-plus	Patch

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (e996aab) to head (eae3b19).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #713   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files           43        43           
  Lines          231       231           
  Branches        51        51           
=========================================
  Hits           231       231           

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