agent-platform release v4.7.6

The portal’s app-config carries no agentPlatform.musterMcpUrl (giantswarm/agent-platform#299): the connectivity chart rendered the platform’s muster MCP URL into the Backstage app-config next to fluxServiceAccountName, but the Dev Portal reads no such key — it creates agents through agent-manager’s tools, and create_agent takes no muster argument. Where muster is reaches agent-manager alone: the meta chart derives its chart value muster.url from the agent-platform.musterMcpUrl helper (unchanged), agent-manager composes it into every agent’s RemoteMCPServer and reports it in get_info. make verify-wiring asserts the key stays gone; verify-identity keeps asserting the agent-manager leg. No installation acts — nothing read the key.