feat(cloud-agent-next): allow workspace backups without setup commands

[eshurakov]

What

Workspace repo snapshots (buildWorkspaceBackupCandidate) required a non-empty setupCommands list. Sessions that only clone a repository — for example code reviews resolved from an explicit profile — therefore never populated or reused the prepared-workspace cache.

This removes that gate. Setup commands remain part of the cache fingerprint, so sessions with different setup recipes keep distinct entries and cannot share a snapshot.

Verification

• pnpm exec vitest run src/workspace-backup-cache.test.ts — 24 passed
• pnpm exec vitest run src/agent-sandbox/cloudflare/cloudflare-agent-sandbox.test.ts — 51 passed
• oxlint on the changed files — clean
• oxfmt --check on the changed files — clean
• tsgo --noEmit — clean

Note: unit tests only. No end-to-end run of a session/code review with snapshots enabled.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (2 files)

• services/cloud-agent-next/src/workspace-backup-cache.ts
• services/cloud-agent-next/src/workspace-backup-cache.test.ts

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_{Reviewed by deepseek-v4.1-flash · Input: 0 · Output: 0 · Cached: 0}

_{Review guidance: REVIEW.md from base branch main}