What type of PR is this?

/kind feature

What this PR does / why we need it:

Fork-only CI validation for the experimental agent-sandbox v0.5.0rc1 / v1beta1 adaptation.

This PR intentionally targets the fork base branch release-agent-sandbox-v05-base so CI only validates the v0.5 rc1 delta on top of the latest volcano-sh#387-compatible baseline. It is not an upstream review request.

Main changes in the delta:

• Update AgentCube imports, schemes, and dynamic GVRs from agent-sandbox v1alpha1 to v1beta1.
• Replace direct Sandbox spec.replicas=1 with spec.operatingMode=Running.
• Replace warm-pool SandboxClaim templateRef usage with required warmPoolRef.
• Update workload-manager, agentd, and e2e tests for the v1beta1 API shape.
• Keep the latest fix: adapt code interpreter warm pool to agent-sandbox v0.4.6 volcano-sh/agentcube#387 review fixes in the base branch, including owner/RLAC propagation and sandbox-create error handling.

Which issue(s) this PR fixes:
Refs local Day18 validation notes only.

Special notes for your reviewer:

• Scope: fork-only CI validation; do not use this as an upstream PR.
• Base: release-agent-sandbox-v05-base at c2633c5, matching the latest fix: adapt code interpreter warm pool to agent-sandbox v0.4.6 volcano-sh/agentcube#387 head.
• Head: test/agent-sandbox-v05-forward at 3abdb94.
• Rebase note: rebased from the older fix: adapt code interpreter warm pool to agent-sandbox v0.4.6 volcano-sh/agentcube#387 baseline 5867183 onto current fix: adapt code interpreter warm pool to agent-sandbox v0.4.6 volcano-sh/agentcube#387 head c2633c5 using rebase --onto; the PR diff remains the two v0.5-specific commits only.
• Local validation after rebase:
  • go test ./pkg/workloadmanager ./cmd/workload-manager ./cmd/agentd -count=1
  • make lint
  • go list ./... | grep -v '^github.com/volcano-sh/agentcube/test/e2e$' | xargs go test -count=1
  • go test ./test/e2e -run '^$' -count=1
  • make gen-check
  • make build-all
  • git diff --check
  • git diff --exit-code
• Prior runtime validation passed before this rebase: direct/warm-pool runtime e2e on a clean k3d cluster with the rc1 manifest, SDK, LangChain, MCP HTTP/stdio, and math-agent LLM e2e.
• Known limitation: this validates clean v1beta1 install behavior. It does not prove in-place CRD migration from clusters whose CRD status still contains storedVersions=["v1alpha1"].
• AI assistance: Used Codex to help inspect code, run validation, and prepare this fork-only CI PR. I reviewed and validated the changes.

Does this PR introduce a user-facing change?:

NONE