docs: update README.es.md

[necropheus]

Improve Spanish README translation naturalness and consistency

Refine several translations to sound more natural in Spanish technical writing. This includes replacing some overly literal translations (eg. "build"), making section titles and wording more idiomatic for software documentation, and fixing inconsistencies in verb forms/tenses across the README.

Also tweak a few phrases that felt unnatural or too directly translated from English.

Issue for this PR

None

Closes #27741

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Improves README.es.md

If you paste a large clearly AI generated description here your PR may be IGNORED or CLOSED!

How did you verify your code works?

It's a readme

Screenshots / recordings

If this is a UI change, please include a screenshot or recording.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.

[github-actions]

Hey! Your PR title Update README.es.md doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍