test: add per-node config differentiation and agent-specific routing tests

Two new integration test suites:

1. Per-node config differentiation (4 tests): label-based rollout
   targeting deploys different bundles to frontend vs backend nodes,
   pinned nodes are excluded from rollouts for other bundles, node
   group targeting limits deployment scope, and direct bundle
   assignment bypasses rollouts for specific nodes.

2. Agent-specific routing (4 tests): services with different plugins
   (WAF, auth, bot-manager) produce per-service agent config in
   generated KDL, services with different middleware stacks (rate-limit,
   CORS, compression) produce distinct configs, generated bundles from
   service definitions deploy to nodes, and per-service plugin config
   overrides produce different agent behavior per endpoint.

Author: raffaelschneider