FailIfMultiNodes hardcodes "talm template" in error message, confusing apply callers #121

Problem

pkg/engine/engine.go:210 calls:

helpers.FailIfMultiNodes(ctx, "talm template")

The string "talm template" is used in the error message: command "talm template" is not supported with multiple nodes. This was accurate when engine.Render was only called from the template subcommand, but after #119 it is also called from apply. A user running talm apply who hits this check will see an error mentioning talm template, which is confusing.

Proposed fix

Thread the caller command name through engine.Options:

type Options struct {
    // ...
    CommandName string // e.g., "talm apply" or "talm template"
}

Then use opts.CommandName in the FailIfMultiNodes call, with a sensible default.

References

• pkg/engine/engine.go:209-213
• Surfaced by fix(commands): render templates online in apply to resolve lookups #119