apply / create -f / update -f should warn on silently-lossy fields before writing

[mmanciop]

The Dash0 API silently drops several categories of client-supplied fields on write — most notably any metadata.labels or metadata.annotations outside the dash0.com/* namespace, but also server-managed timestamps (dash0.com/created-at, dash0.com/updated-at) and derived id/origin labels the caller cannot set.

The CLI's write paths (apply, create -f, update -f across every domain) currently forward the document as-is. The user gets a "created" or "updated" success, but their intent — say, metadata.labels.team-lead: alice — is silently dropped.

Current behavior

$ cat team.yaml
apiVersion: dash0.com/v1alpha1
kind: Dash0Team
metadata:
  name: backend
  labels:
    team-lead: alice        # will be silently dropped
    dash0.com/origin: git   # ok
spec:
  display:
    name: Backend
    color: {from: "#000", to: "#FFF"}
  members: []

$ dash0 apply -f team.yaml
Team "Backend" created (id: team_01…).
$ dash0 -X teams get team_01… -o yaml | yq .metadata.labels
dash0.com/id: team_01…
dash0.com/origin: git
dash0.com/source: cli
# team-lead: alice — silently gone

No warning, no diagnostic, no non-zero exit. A user who then exports the team, edits the description, and re-applies has lost their custom label entirely with no signal at any step.