feat: allow Pipeline authors to override Task compute resources

[waveywaves]

Changes

Adds stepSpecs, sidecarSpecs, and computeResources fields to PipelineTask,
allowing Pipeline authors to override the referenced Task's resource requirements
without duplicating the Task or requiring users to specify taskRunSpecs in every
PipelineRun.

The problem

Today, resource overrides are only possible at:

• Task level: Task.spec.steps[].computeResources (set by the task author)
• PipelineRun level: PipelineRun.spec.taskRunSpecs[].computeResources (set by the user at runtime)

There is no way for a Pipeline author to override resources at definition time. This forces
pipeline authors to either duplicate tasks with different resource values or require users to
specify taskRunSpecs in every PipelineRun — both of which are poor UX as demonstrated by
recent Konflux issues where users had to override resources for dozens of individual .tekton
files.

The solution

apiVersion: tekton.dev/v1
kind: Pipeline
spec:
  tasks:
    - name: build
      taskRef:
        name: buildah
      # NEW — override the referenced Task's resource requirements
      computeResources:
        requests:
          memory: 4Gi
      stepSpecs:
        - name: build
          computeResources:
            requests:
              memory: 8Gi
            limits:
              memory: 16Gi

Precedence chain: Task defaults < Pipeline PipelineTask overrides < PipelineRun taskRunSpecs overrides

This mirrors how timeout already works on PipelineTask — Pipeline sets a default, PipelineRun
can override it.

Implementation

• API: Added StepSpecs, SidecarSpecs, ComputeResources fields to PipelineTask in
  pkg/apis/pipeline/v1/pipeline_types.go
• Reconciler: In createTaskRun(), Pipeline-level values are set first, then PipelineRun-level
  taskRunSpecs override them if specified (pkg/reconciler/pipelinerun/pipelinerun.go)

TODO (follow-up commits)

• Generated code (hack/update-codegen.sh)
• Validation in pipeline_validation.go
• Variable substitution support
• Unit tests for precedence chain
• E2E test
• Documentation updates

Related Issues

• Closes feat: allow Pipeline authors to override Task compute resources at the PipelineTask level #9630
• Related to TEP-0104 (Task-level resource requirements)
• Directly addresses Konflux OOMKilled issues where users couldn't override resources at the Pipeline level

Submitter Checklist

• Has Docs if any changes are user facing
• Has Tests included if any functionality added or changed
• pre-commit Passed
• Follows the commit message standard
• Meets the Tekton contributor standards including completing the contributor CLA
• Each commit in the PR has a meaningful subject line and body

Release Note

Pipeline authors can now override Task compute resources (stepSpecs, sidecarSpecs,
computeResources) at the PipelineTask level, eliminating the need to duplicate Tasks
or require users to specify taskRunSpecs in every PipelineRun.

[tekton-robot]

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