fix(planner): resolve aggregate workers by component type (cherry-pick #11578)

[dagil-nvidia]

Summary

Clean cherry-pick of #11578 onto release/1.4.0 (no conflicts, 2 files, +58).

• Resolve aggregate planner workers by their DGD component type instead of backend-specific names.
• Treat the sole generic type: worker component as the planner's decode component, regardless of its name.
• Keeps the existing explicit-name fallback when multiple generic workers make the type ambiguous.

Fixes the planner bug reported in #12384 for the 1.4.0 release. Original PR merged to main on 2026-07-30 (d66670faaa).

🤖 Generated with Claude Code

---

[devin-ai-integration]

Devin Review found 1 potential issue.

[devin-ai-integration]

🟡 Explicitly configured decode worker can be ignored in favour of a differently-named worker

The lone generic worker is picked as the decode worker (generic_workers check at components/src/dynamo/planner/monitoring/dgd_services.py:213-220) before the explicitly configured worker name is even looked at, so the planner can scale a worker the operator never asked it to scale.
Impact: In a deployment that names its decode worker explicitly while another worker is only generically labelled, the planner resizes the wrong worker group, breaking autoscaling for the intended one.

Precedence between type-based fallback and explicit component name

In get_component_from_type_or_name, the new block runs before the component_name in components branch (components/src/dynamo/planner/monitoring/dgd_services.py:222-226). Consider a v1beta1 DGD with component A of type: worker (actually prefill) and component B with no type field, where the caller passes component_name="B" for SubComponentType.DECODE. No component has type: decode, so matching_components is empty; the fallback finds exactly one generic worker (A) and selects it, and the explicit-name branch is skipped. Previously B would have been selected via _can_use_explicit_component_name (which explicitly permits an empty type, see components/src/dynamo/planner/monitoring/dgd_services.py:88-96). All callers that pass decode_component_name (components/src/dynamo/planner/connectors/kubernetes.py:236-240, :660-664, :700-704) are affected, including replica updates.

A safer ordering is to try the explicit name first and only use the sole-generic-worker fallback when no usable explicit name is given.

Suggested change

	if not matching_components and component_type == SubComponentType.DECODE:
	generic_workers = [
	(name, component)
	for name, component in components.items()
	if get_component_type(component) == V1BETA1_GENERIC_WORKER_COMPONENT_TYPE
	]
	if len(generic_workers) == 1:
	matching_components = generic_workers
	if (
	not matching_components
	and component_type == SubComponentType.DECODE
	and component_name not in components
	):
	generic_workers = [
	(name, component)
	for name, component in components.items()
	if get_component_type(component) == V1BETA1_GENERIC_WORKER_COMPONENT_TYPE
	]
	if len(generic_workers) == 1:
	matching_components = generic_workers

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[dagil-nvidia]

/ok to test fc1c966