Test Coverage: Expand coverage checks and reporting

[shaneutt]

Ideally, we should expand our CI to better report test coverage and gate PRs on ensuring the changes are covered by tests.

[esnible]

We have a make coverage target that reports our codebase is 30.6% covered by unit tests.

We should try to at least double that.

FYI we also have make htmlcov which will show the unit test code coverage by file and line.

I asked Claude Code and it suggested that we need more tests a few places:

Files with NO Tests (Critical Gaps)

File	Lines	Description
pkg/controller/mcpserver_controller.go	988	Main Kubernetes reconciliation logic
pkg/controller/config_writer.go	97	ConfigMap/Secret persistence
pkg/controller/server_validator.go	110	Server health validation
internal/broker/oauth_protected_resource_handler.go	109	OAuth discovery endpoint

Files with Insufficient Test Coverage

File	Lines	Test Lines	Coverage
internal/mcp-router/server.go	167	2	~1% (test file is empty)
internal/mcp-router/headers.go	159	44	~28%
internal/broker/broker.go	947	374	~39%