[13.x] Fix examples and descriptions that don't match framework behavior - #11387

A few examples and descriptions in the docs don't match the behavior of Laravel 13.x. I checked each case against the framework.

In validation.md, the comment for Password::min(8)->uncompromised(3) says the password must have appeared less than 3 times. NotPwnedVerifier only fails when the count is greater than the threshold, so a password seen exactly 3 times still passes.

The online index example in migrations.md also doesn't produce the result shown. Chaining ->online() after ->unique() on the column definition doesn't add the CONCURRENTLY flag. Applying online() to the index definition does:

$table->unique('email')->online();

In pagination.md, the User::paginate() JSON example includes current_page_url, but LengthAwarePaginator::toArray() doesn't return that key. That key is present on the simple Paginator instead.

Finally, requests.md says that integer() uses the default when the cast fails. The method uses a plain (int) cast, so a non-numeric value becomes 0; the default is only used when the input is missing.

?per_page=abc  -> integer('per_page', 15) => 0
missing        -> integer('per_page', 15) => 15

These examples and descriptions are updated to match the actual 13.x behavior.