[Manual Sync Required] feat(runner): SandboxV2 sandbox management with WarmPool and idle auto-reclaim

[Rader]

Summary:

• Introduces SandboxV2 management for the Runner, implementing full sandbox lifecycle control, a WarmPool, and shared PVC with subPath isolation based on the agent-sandbox v0.5.4 SDK.
• Implements idle auto-reclaim logic that deletes ephemeral sandboxes after 10 minutes and suspends persistent ones after 24 hours, featuring TOCTOU double-checking, startup grace periods, and WarmPool protection to prevent premature deletion.
• Switches Suspend/Resume operations to MergePatch to avoid resourceVersion conflicts, and migrates from Director to Rewrite.

Manual handling required:

• Dev-agent failed to cherry-pick this GitLab MR: MR 包含 merge commit，自动 cherry-pick 需要 -m 主线选择，改为创建人工处理 PR
• Source GitLab MR: !2859
• Source ref: 50ae60ed0920bd0b4b90f11b7e4d044927d0063e
• Files in sync scope: 10
• The patch could not be applied cleanly, so this branch uses the GitLab MR final file snapshot for the affected files. Please reconcile any overwritten GitHub-side edits before merging.