Reduce bootstrap k8s cluster to single node (k3d agents=0)

[rowan-stein]

User request

Reduce Kubernetes node count in bootstrap to a single node to see if it reduces provisioning time and overall resource consumption.

Specification (from research)

Bootstrap provisions a local k3d/k3s cluster via Terraform stack stacks/k8s (provider agynio/k3d). Current defaults are:

• servers = 1
• agents = 2

Target single-node Kubernetes cluster:

• servers = 1
• agents = 0

Required changes

1. Default node counts

   • In stacks/k8s/variables.tf, change agents default from 2 to 0.
   • Add validations:
     • servers >= 1
     • agents >= 0

2. Make node count explicit in bootstrap apply flow

   • In apply.sh, for the k8s stack, pass -var servers=... and -var agents=... using environment variables:
     • K3D_SERVERS (default 1)
     • K3D_AGENTS (default 0)
   • Add basic integer validation for these env vars (similar to existing PORT validation).

3. Expose node count as action inputs (CI)

   • In .github/actions/provision/action.yml, add inputs:
     • servers default "1"
     • agents default "0"
   • Wire them to the apply.sh step via env vars (K3D_SERVERS, K3D_AGENTS).

4. Verification

   • Add a post-provision assertion (in existing health verification step or a small new script step):
     • kubectl get nodes --no-headers | wc -l must equal 1.
   • Also log node taints for debugging if scheduling fails.

5. Metrics for comparison (time/resources)

   • Ensure CI logs include (best-effort):
     • apply.sh timing summary (already present)
     • docker system df and df -h before/after provisioning
     • kubectl get nodes -o wide and kubectl get pods -A -o wide
   • These metrics should enable baseline comparison between agents=2 and agents=0 runs.

Acceptance criteria

• Default bootstrap provisions exactly 1 Kubernetes node.
• Existing platform verification (e.g., health checks) still passes.
• CI remains green.
• Logs (or artifacts, if already used) include enough timing/resource data to compare against the prior 3-node topology.

Notes / constraints

• k3d load balancer container will still exist; success is 1 Kubernetes node, not 1 Docker container.
• This is intended for bootstrap/CI/local usage (not HA).

[rowan-stein]

Closing per request (PR #507 was closed and no changes were merged).