fix: Node level lazy parameter fix

[TannerGilbert]

🦟 Bug fix

Fixes #751

Summary

Fix the lazy ROS parameter on the parameter_bridge and RosGzBridge nodes so it actually works as a global default for all bridge topics.

What was broken:

• parameter_bridge.cpp declared and read the lazy parameter but never applied it to bridge configs — it was a dead variable
• RosGzBridge (used for YAML config and parameter-based bridges) never declared a lazy parameter at all, so YAML-loaded bridges always defaulted to lazy: false

What this PR does:

• Changes BridgeConfig::is_lazy from bool to std::optional so we can distinguish "not set" from "explicitly set to false"
• The node-level lazy parameter now serves as the default for all bridges that don't explicitly set lazy per-entry in YAML
• Per-entry lazy: true or lazy: false in YAML overrides the node-level default
• Applies lazy to CLI-specified bridges in parameter_bridge as well

Behaviour:

Node-level lazy	Per-entry YAML lazy	Resolved value
false (default)	not set	false
false (default)	true	true
false (default)	false	false
true	not set	true
true	true	true
true	false	false

Checklist

• Signed all commits for DCO
• Added a screen capture or video to the PR description that demonstrates the fix (as needed)
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• Updated Bazel files (if adding new files). Created an issue otherwise.
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[ahcorde]

Suggested change

	}
	// Verify that BridgeHandle::IsLazy() falls back to kDefaultLazy when
	// BridgeConfig::is_lazy is std::nullopt, and returns the explicit value
	// when it is set.
	TEST(BridgeHandleIsLazy, NulloptFallsBackToDefault)
	{
	ros_gz_bridge::BridgeConfig config;
	config.is_lazy = std::nullopt;
	// IsLazy() must return the hard-coded default when no value is set.
	EXPECT_EQ(ros_gz_bridge::kDefaultLazy, config.is_lazy.value_or(ros_gz_bridge::kDefaultLazy));
	}
	TEST(BridgeHandleIsLazy, ExplicitTrueIsRespected)
	{
	ros_gz_bridge::BridgeConfig config;
	config.is_lazy = true;
	EXPECT_TRUE(config.is_lazy.value_or(ros_gz_bridge::kDefaultLazy));
	}
	TEST(BridgeHandleIsLazy, ExplicitFalseIsRespected)
	{
	ros_gz_bridge::BridgeConfig config;
	config.is_lazy = false;
	EXPECT_FALSE(config.is_lazy.value_or(ros_gz_bridge::kDefaultLazy));
	}

[ahcorde]

Suggested change

	void RosGzBridge::add_bridge(const BridgeConfig & input_config)
	{
	// Resolve the laziness: if the caller left is_lazy as nullopt, inherit the
	// node-level "lazy" parameter so that the effective value is always explicit.
	BridgeConfig config = input_config;
	if (!config.is_lazy.has_value()) {
	bool node_lazy = kDefaultLazy;
	this->get_parameter("lazy", node_lazy);
	config.is_lazy = node_lazy;
	}
	bool gz_to_ros = false;