Fix fleetctl apply ignoring spec.fleet (#44894)

**Related issue:** Resolves #44892

Claude also added tests, since this wasn't covered before, but I've kept
them in a separate commit in case they're not needed.

# Checklist for submitter

## Testing

- [x] Added/updated automated tests
- [ ] QA'd all new/changed functionality manually

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Improved spec parsing to correctly accept resources declared as either
team or fleet, handling nested spec keys consistently and preserving
backward-compatible behavior.

* **Tests**
* Added and updated tests and fixtures to validate parsing across both
team/fleet variants and to assert specific conflict/reporting behavior
when both keys are present.

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---------

Co-authored-by: Scott Gress <scott@fleetdm.com>

cmd/fleetctl/fleetctl/apply_test.go

@@ -318,13 +318,13 @@ func TestApplyTeamSpecs(t *testing.T) {
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team2
 ---
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     agent_options:
       config:
         views:
@@ -375,7 +375,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     mdm:
       windows_updates:
@@ -407,7 +407,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     mdm:
       macos_settings:
@@ -449,7 +449,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     agent_options:
       config:
         views:
@@ -507,7 +507,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     agent_options:
     name: team1
     mdm:
@@ -528,7 +528,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     mdm:
       macos_updates:
@@ -543,7 +543,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     mdm:
       macos_updates:
@@ -604,7 +604,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     webhook_settings:
       host_status_webhook:
@@ -635,7 +635,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     webhook_settings:
 `,
@@ -658,7 +658,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     integrations:
       google_calendar:
@@ -681,7 +681,7 @@ spec:
 apiVersion: v1
 kind: fleet
 spec:
-  team:
+  fleet:
     name: team1
     integrations:
       google_calendar:

pkg/spec/spec.go

@@ -234,7 +234,12 @@ func GroupFromBytes(b []byte, options ...GroupFromBytesOpts) (*Group, error) {
 			if err := yaml.Unmarshal(s.Spec, &rawTeam); err != nil {
 				return nil, fmt.Errorf("unmarshaling %s spec: %w", kind, err)
 			}
+			// Support `team` (for backwards compatibility) but defer to `fleet` if available.
 			teamRaw := rawTeam["team"]
+			if fleetRaw, ok := rawTeam["fleet"]; ok {
+				teamRaw = fleetRaw
+			}
+
 			var err error
 			teamRaw, deprecatedKeysMap, err = rewriteNewToOldKeys(teamRaw, fleet.TeamSpec{})
 			if err != nil {

pkg/spec/spec_test.go

@@ -460,3 +460,66 @@ func TestRewriteNewToOldKeys(t *testing.T) {
 		assert.Equal(t, "fleet", conflictErr.New)
 	})
 }
+
+func TestGroupFromBytesTeamKinds(t *testing.T) {
+	tests := []struct {
+		name string
+		in   []byte
+	}{
+		{
+			"kind: team with team: key",
+			[]byte(`
+apiVersion: v1
+kind: team
+spec:
+  team:
+    name: macOS
+`),
+		},
+		{
+			"kind: fleet with fleet: key",
+			[]byte(`
+apiVersion: v1
+kind: fleet
+spec:
+  fleet:
+    name: macOS
+`),
+		},
+		{
+			"kind: fleet with team: key",
+			[]byte(`
+apiVersion: v1
+kind: fleet
+spec:
+  team:
+    name: macOS
+`),
+		},
+		{
+			"kind: team with fleet: key",
+			[]byte(`
+apiVersion: v1
+kind: team
+spec:
+  fleet:
+    name: macOS
+`),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			g, err := GroupFromBytes(tt.in)
+			require.NoError(t, err)
+			require.Len(t, g.Teams, 1)
+			require.NotNil(t, g.Teams[0])
+
+			var team map[string]json.RawMessage
+			require.NoError(t, json.Unmarshal(g.Teams[0], &team))
+			name, ok := team["name"]
+			require.True(t, ok)
+			assert.Equal(t, `"macOS"`, string(name))
+		})
+	}
+}