Add command so agents can register a new workload on the gateway

[lluisinthedesert]

Problem

The OSS CLI has workloads route to configure traffic routing for an existing workload, but no workloads create command to register a new workload on the gateway. This blocks the end-to-end flow described in skills/use-understudy-gateway/SKILL.md:

1. An agent runs understudy capture-evidence workload-card → local workload-card.json is created ✅
2. Agent tries to route traffic: understudy workloads route workload-001 --model-id gemma-4-31b-it --traffic-pct 100 → 404 "Workload not found" ❌
3. The workload was never registered on the gateway server.

Current behavior

$ understudy workloads route workload-001 --project-id proj_xxx --model-id gemma-4-31b-it --traffic-pct 100
error: Workload not found.

The workload-card.json exists locally but the gateway has no record of it.

Expected behavior

# Register the local workload card on the gateway
understudy workloads create --project-id proj_xxx --from-card .understudy/workload-discovery/workload-card.json

# Then route traffic to it
understudy workloads route workload-001 --project-id proj_xxx --model-id gemma-4-31b-it --traffic-pct 100

Impact

Without this, an agent using only the OSS CLI cannot:

• Set up a workload route through the gateway
• Use understudy run with the gateway to drive an eval against an Understudy model
• Follow the A/B model routing recipe in the skill

The workaround is to either use the private CLI (which has automationbench run-official --provider lilac that handles this internally) or bypass the gateway entirely and call a provider API directly.

Related

• skills/use-understudy-gateway/SKILL.md — describes the workload route flow but assumes a workload exists
• src/commands/workloads.ts — current implementation has only route subcommand
• Add agent config files (opencode.json, .claude/, CLAUDE.md, .codex/) for skill discoverability #35 — agent config discoverability issue

Suggested implementation

Add a workloads create subcommand to src/commands/workloads.ts that:

1. Reads a local workload-card.json
2. Calls the gateway API to register the workload
3. Returns the server-assigned workload-id for use with workloads route

[Dipxssi]

Hey ! @lluisinthedesert
I'm working on this PR and will submit the implementation soon.