fix(docs): correct cookie counter example fallback

[caduvt]

Fixes inconsistencies in the first example of "Cookie" page, in playground. A more detailed explanation of the problem is given in the issue.

https://elysiajs.com/tutorial/patterns/cookie/

Fixes #851

Summary by CodeRabbit

• Documentation
  • Updated the cookie pattern tutorial with improved code examples demonstrating clearer and more maintainable approaches to handling cookie values.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 13798944-85ba-426b-9847-5f9adcdaa4b8

📥 Commits

Reviewing files that changed from the base of the PR and between b8eced1 and 71f21da.

📒 Files selected for processing (1)

• docs/tutorial/patterns/cookie/index.md

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Walkthrough

The cookie pattern tutorial example is corrected to handle undefined values properly. The counter update now explicitly converts the cookie value using Number() and assigns the incremented result, fixing the previous logic where unary coercion occurred before the nullish coalescing operator, causing NaN fallback instead of 0.

Changes

Cookie Example Documentation Fix

Layer / File(s)	Summary
Cookie counter fallback correction docs/tutorial/patterns/cookie/index.md	Counter logic updated from const total = +visit.value ?? 0 and visit.value++ to const total = Number(visit.value ?? 0) and visit.value = total + 1, properly handling undefined values with correct operator precedence.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

✨ A cookie so sweet, yet undefined before ♡~
NaN was lurking, but now it's fixed for sure~ (´▽｀)
Zero falls back when the value's not there~
Your counter's now safe, no more bugs to spare~ ♡

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(docs): correct cookie counter example fallback' directly and accurately describes the main change—fixing the cookie counter example's fallback logic.
Linked Issues check	✅ Passed	The PR correctly addresses issue #851 by rewriting the counter update logic to use Number(visit.value ?? 0) instead of +visit.value ?? 0, properly handling the fallback when the cookie is undefined.
Out of Scope Changes check	✅ Passed	The changes are limited to the cookie example documentation, directly addressing the fallback bug described in issue #851 with no extraneous modifications.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

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