Merge links into nodes: Create link output from link solver algorithm

[figueroa1395]

Part of #35

Follow up of #1536

This PR should activate the Link output with two paths (old and new) + add the steady state output for i

[nitbharambe]

Rest looks good

[Copilot]

Pull request overview

Adds link outputs for merged-node topology while retaining legacy output behavior.

Changes:

• Generates steady-state and short-circuit link outputs.
• Includes shunts and three-winding transformers in link-flow balancing.
• Adds component traits and expanded unit tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
topological_node_output.hpp	Accumulates grid flows and generates link outputs.
output.hpp	Routes legacy and merged-topology link outputs.
container.hpp	Exposes stored component types.
test_topological_node_output.cpp	Tests flow accumulation and link solving.
test_main_core_output.cpp	Tests link output conversion.

Suppressed comments (2)

power_grid_model_c/power_grid_model/include/power_grid_model/main_core/output.hpp:147

• The short-circuit path repeats the incorrect energized test: it marks a supplied one-sided link off and a closed link in an unsupplied island on. Guard a disconnected topo_id, then use state.topo_comp_coup->node[topo_id.group] to determine source connectivity, matching the legacy branch path and Edge::energized semantics.

    if (!link.edge_status() || topo_id.group == disconnected) {

tests/cpp_unit_tests/main_core/test_main_core_output.cpp:285

• As in the steady-state case, a link with one active terminal connected to a source should remain energized; only its flow is zero. This status_off expectation conflicts with Edge::energized and with the old output path. Add supplied node-to-math coupling to the fixture and expect IntS{1}.

            CHECK(output[1].id == 1);
            CHECK(output[1].energized == status_off);

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[mgovers]

i realized that there's no test case checking link energized. as a result, we almost introduced a bug in this PR in which a link connected only on one side to source would be marked "energized": 0. That is of course incorrect. Its p_(from|to) and q_(from|to) should be 0 but not the energized. Hence I added this validation case

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
98.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[nitbharambe]

do-not-merge added since its friday. Rest looks good