refactor(cloud/scale): Migrate final errors to typed vars

[robaa12]

Prerequisite checklist

• Read the contribution guidelines regarding submitting new changes to the project;
• Tested your changes locally.

Description of changes

This PR is a scoped, file-by-file contribution toward #102 , limited to the cloud/scale command package.
It converts non-wrapped final errors to file-local typed errors (var Err... = errors.New(...)) in the following files:

• internal/cli/kraft/cloud/scale/add/add.go
• internal/cli/kraft/cloud/scale/remove/remove.go
• internal/cli/kraft/cloud/scale/get/get.go
• internal/cli/kraft/cloud/scale/reset/reset.go
• internal/cli/kraft/cloud/scale/initialize/initialize.go

What was changed:

• Replaced final fmt.Errorf("...") returns with typed error vars where applicable.
• Kept wrapped operational/contextual errors (...: %w) unchanged.
• In some cases, preserved extra runtime context while wrapping typed errors (for future errors.Is(...) checks).

Validation:

• go test ./internal/cli/kraft/cloud/scale/...
• go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@v2.11.4 fmt
  Notes:
• Commits are intentionally split one file at a time to keep review and git bisect/blame clean.
• This PR partially addresses Migrate all errors to constants #102.

[craciunoiuc]

These should be moved to a separate file at on the cloud directory I think right?

[robaa12]

So you mean creating an errors.go file at the package level? I actually thought about doing that, but I saw this comment and went with a different approach:
#102 (comment)

Just to confirm I got it right the idea is to define all error constants in errors.go, then import and use them across the package?

[craciunoiuc]

Yes

Though you won't import them if they are in the same package.

There are two possible options. I'm fine with both:

• You populate the Errors at the top of each file and use them only in there
• You populate them into an errors.go in every package

[robaa12]

I think the second approach is cleaner. I’ll start adding it to the cloud package and go from there.

[robaa12]

Hey @craciunoiuc
I moved typed error declarations out of the command files and into package-level errors.go files for each touched cloud/scale subpackage:

• internal/cli/kraft/cloud/scale/add/errors.go
• internal/cli/kraft/cloud/scale/remove/errors.go
• internal/cli/kraft/cloud/scale/get/errors.go
• internal/cli/kraft/cloud/scale/reset/errors.go
• internal/cli/kraft/cloud/scale/initialize/errors.go

I also removed the inline error variable blocks from the corresponding command files. Behavior remains unchanged, including %w wrapping and existing context where applicable.

Follow-up

For follow-up work, I plan to continue this migration in small, package-scoped PRs across the codebase.