agent-platform release v0.5.0

agentic-platform-mcps bundled as a conditional sub-chart (condition: mcps.enabled, default false). It renders the platform’s MCP server CRs (muster MCPServer and/or agentgateway AgentgatewayBackend + AgentgatewayPolicy) from one abstract agentic-platform-mcps.mcpServers list. The toggle lives in a separate top-level mcps: block because the sub-chart’s strict values.schema.json (additionalProperties: false) rejects an enabled key. The CRs consume CRDs shipped by the companion agentic-platform-crds chart — the umbrella still installs zero CRDs. New ci/test-mcps-values.yaml exercises the path.