[fix] Use transient workflows for draft previews

[rishabh-chawla-glean]

Problem

Replicate the preview-link/transient-workflow portion of https://github.com/askscio/scio/pull/245939/changes. Draft previews were being created through the normal agent sync path and PR comments linked to the real agent edit URL, so preview comments could point at the wrong workflow instead of the server-created transient preview.

Solution

• Add preview request builders for workflow and automode agents that create transient workflows via POST /rest/api/v1/agents.
• Link transient previews back to the real agent using parentWorkflowId and force workflowNamespace: "AGENT".
• Keep staged/published syncs on POST /rest/api/v1/agents/{id}.
• Capture the server-assigned transient workflow id as previewId.
• Update PR comments to link to /chat/agents/{previewId}/preview, falling back to the agent id if no preview id is present.

Tests

• bash -n scripts/sync-agents.sh scripts/comment-pr.sh scripts/comment-merge.sh scripts/detect-changes.sh scripts/github_output.sh
• Mocked workflow-agent preview sync verifying request URL, transient request body, and previewId result.
• Mocked PR comment rendering verifying /preview link uses the transient preview id.

  

[harshita-boonlia-glean]

@rishabh-chawla-glean can we test this with a git agent post merge