feat(cli): add langgraph deploy logs subcommand

[Vishnu Suresh (vishnu-ssuresh)]

Add a langgraph deploy logs subcommand to fetch build and deploy/server logs from LangSmith deployments.

Changes

• host_backend.py: Add get_build_logs() and get_deploy_logs() methods, plus langsmith_url support.
• helpers.py (new): Log formatting (format_log_entry, format_timestamp, level_fg) and resolution helpers (resolve_deployment_id).

Usage

# Deploy logs (latest 10)
langgraph deploy logs --deployment-id <id> --limit 10

# Error logs by name
langgraph deploy logs --name gtm-agent --level ERROR

# Build logs
langgraph deploy logs --deployment-id <id> --type build

# Tail logs (Ctrl+C to stop)
langgraph deploy logs --name gtm-agent --follow

Tests

56 unit tests passing covering host backend methods, log formatting, and helper functions.

[Andrew Nguonly (andrewnguonly)]

How come we're not using the offset/next_offset pagination for tailing logs?

[Andrew Nguonly (andrewnguonly)]

Why is this removed?

[hari-dhanushkodi]

its not used in any of the helper functions, we just use it to set the header

[hari-dhanushkodi]

How come we're not using the offset/next_offset pagination for tailing logs?

as discussed offline, I think this is the best way to implement live tail:

1. first we fetch last limit logs in descending (so we get newest -> oldest in an array)
2. we output the reverse of the output of step 1 (so that old logs appear first, and new logs come to the front)
3. then we do an ascending log fetch with the most recent time stamp we got in step 1, so we don't fetch anything older than this, and we output to the screen and repeat