docs(uuid): fix stale v1 JSDoc and remove unnecessary casts from examples

[tomas-zijdemans]

Fixes doc rot in @std/uuid left behind by an old API change. No code changes.

v1.generate() used to return string | number[]. The union is long gone, but three traces of it survived:

• Two {@linkcode V1Options.*} references in v1.ts point at an interface that was renamed to GenerateOptions, so the links render dead on JSR.
• The @returns doc still says "a UUIDv1 string or an array of 16 bytes". It returns a string.
• Four examples (v1, v6, and two in mod.ts) cast validate(uuid as string). The casts are no-ops now, and they teach readers to distrust a return type that is plain string.

All doc examples still compile and pass: deno test --doc uuid/ is green, 66 tests.

I used Claude Code to help investigate and write this change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.03%. Comparing base (ca58f94) to head (78c0195).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7285      +/-   ##
==========================================
- Coverage   95.03%   95.03%   -0.01%     
==========================================
  Files         617      618       +1     
  Lines       51637    51892     +255     
  Branches     9359     9408      +49     
==========================================
+ Hits        49075    49316     +241     
- Misses       2021     2030       +9     
- Partials      541      546       +5     

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