render: Sync render.proto with c/c and wire XRD through

[jcogilvie]

Description of your changes

Two commits:

1. proto: Sync render.proto with crossplane/crossplane main — adds composite_resource_definition (field 8) to CompositeInput, matching the upstream proto, and regenerates render.pb.go via ./nix.sh run .#generate (Nix-pinned protoc-gen-go v1.36.10). The cli's option go_package intentionally still points at github.com/crossplane/cli/v2/proto/render/v1alpha1; after that one line the proto file is byte-identical to upstream main.

2. render: wire CompositionInputs.XRD through to the proto — adds an XRD *unstructured.Unstructured field to CompositionInputs and threads it through BuildCompositeRequest to the proto's CompositeResourceDefinition. When the caller leaves XRD nil, behavior is unchanged: the field stays unset and the render binary keeps its Schema=Modern fallback. This mirrors the Go-level change in crossplane/crossplane/cmd/crossplane/render so the cli's CompositionInputs stays in sync with what the binary now consumes.

Picking up an XRD from disk / the --extra-resources flag and populating CompositionInputs.XRD at the call sites (e.g. cmd/crossplane/render/xr/cmd.go) is intentionally out of scope here — that's a separate UX-shaped change. After this PR the plumbing is in place; the field is available to any caller that wants to use it.

Upstream proto changes:

• crossplane/crossplane@12f3f1c (adds the field; composite_resource_definitions plural at the time)
• crossplane/crossplane@babb251 (review feedback: collapses to singular composite_resource_definition; this PR matches the post-feedback shape on main)

How this is covered by tests: regen is mechanical, and the wiring commit is pure plumbing — leaving CompositionInputs.XRD nil produces the same proto request as before, so the existing cmd/crossplane/render/... tests cover the no-XRD path. ./nix.sh flake check passes.

Fixes #

I have:

• Read and followed Crossplane's contribution process.
• Run ./nix.sh flake check to ensure this PR is ready for review.
• Added or updated unit tests. Regen + nil-default plumbing; the existing render tests cover the unchanged no-XRD path. Happy to add a test that asserts the XRD-set path produces the populated proto field if reviewers want it.
• Linked a PR or a docs tracking issue to document this change. No user-facing change yet — this PR adds the proto field and the CompositionInputs.XRD plumbing; there's no command-surface change to document.
• Added backport release-x.y labels to auto-backport this PR. Not a backport candidate; happy to add a label if maintainers want it on a release branch.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR extends the CompositeInput protobuf message with an optional composite_resource_definition field. This field carries the XRD (composite resource definition) used to determine whether the renderer should apply Legacy or Modern schema behavior, with Modern schema as the default fallback.

Changes

CompositeInput Schema Extension

Layer / File(s)	Summary
Composite resource definition field addition proto/render/v1alpha1/render.proto	The CompositeInput message adds an optional google.protobuf.Struct composite_resource_definition field (tag 8) with documentation explaining it supplies the XRD for schema behavior selection and that Schema=Modern is the fallback when absent.

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Breaking Changes	✅ Passed	PR modifies only proto files outside apis//cmd/, adding optional field with no removals or required additions to public entities.
Feature Gate Requirement	✅ Passed	The new field is in proto/ (not apis/**), is optional with fallback behavior, doesn't affect existing behavior, and isn't marked experimental. No feature gate required.
Description check	✅ Passed	The description is comprehensive and directly related to the changeset, detailing both commits, the proto field addition, the wiring changes, and test coverage.
Title check	✅ Passed	The title clearly describes the main change: syncing the render.proto file with upstream and adding the XRD field, directly matching the PR's core objective.

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[adamwg]

lgtm, thanks for taking care of this.

[github-actions]

Successfully created backport PR for release-2.3:

• [Backport release-2.3] render: Sync render.proto with c/c and wire XRD through #78