test: add e2e regression tests for router graceful shutdown

[raballew]

Summary

• Adds e2e regression tests verifying the router deployment configuration prevents the failure patterns described in Updating the router kills existing connections #28
• Tests cover rollout strategy (maxUnavailable=0, maxSurge>=1), readiness/liveness probes, preStop hook for connection draining, terminationGracePeriodSeconds, and health probe parity with the controller deployment
• These tests will fail until the router deployment spec is updated to include graceful shutdown support

Closes #28

Test plan

• Verify tests compile against the existing e2e suite
• Run tests against a cluster with the current router deployment (expect failures documenting the gaps)
• Run tests after implementing the router graceful shutdown changes (expect pass)

🤖 Generated with Claude Code

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