feat(chart): add extraInitContainers, extraContainers, extraVolumeMounts, extraVolumes support

[chaodu-agent]

Summary

This PR adds four extension points to the Helm chart deployment template, allowing users to inject custom resources without modifying the chart itself.

Key Changes

• extraInitContainers — inject init containers that run before the main openab container (e.g., fetch secrets from Vault, pull config from S3, wait for dependencies)
• extraContainers — add sidecar containers alongside the main container (e.g., MCP tool servers, log forwarders, token refreshers)
• extraVolumeMounts — mount additional volumes into the main container (e.g., Secret-based credentials, shared config)
• extraVolumes — declare additional volumes for the pod (PVC, Secret, ConfigMap, emptyDir)

Example Usage

agents:
  kiro:
    extraVolumes:
      - name: mcp-socket
        emptyDir: {}
    extraVolumeMounts:
      - name: mcp-socket
        mountPath: /tmp/mcp
    extraContainers:
      - name: my-mcp-server
        image: ghcr.io/myorg/my-mcp-tools:latest
        volumeMounts:
          - name: mcp-socket
            mountPath: /tmp/mcp

Design

• Follows the standard Helm extra* pattern (with + toYaml + nindent)
• All four fields default to [] — zero impact on existing deployments
• Per-agent scoped (under agents.<name>), so each agent can have its own extensions
• Placement in deployment.yaml:
  • extraInitContainers: before containers:
  • extraVolumeMounts: after the tmp mount in the main container
  • extraContainers: after the main container
  • extraVolumes: after the tmp emptyDir volume

[github-actions]

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