Fix MLD search functions to return unpacked edges

[Claude]

The MLD search wrapper was discarding pre-computed unpacked edges, forcing callers to recreate them via redundant facade.FindEdge() lookups. This eliminated work already done during the search phase.

Changes

• Updated MLD search wrapper (routing_base_mld.hpp): Added unpacked_edges parameter to return both nodes and edges from search
• Added unpackPath overload: Accepts pre-computed edges to bypass FindEdge() calls
• Modified shortest path implementation (shortest_path_impl.hpp):
  • Updated searchWithUTurn and multi-candidate search to handle edges
  • Modified route_state structure to track edges alongside nodes
  • Updated unpackLegs to use pre-computed edges via new unpackPath overload
  • Adapted shortestPathWithWaypointUTurns and shortestPathWithWaypointContinuation for edge storage
• Updated unit test wrapper (offline_facade.cpp): Matched new signature

Example

Before:

// Search computes edges but discards them
auto unpacked_path = search(...);
weight = unpacked_path.weight;
unpacked_nodes = std::move(unpacked_path.nodes);
// unpacked_path.edges discarded!

// Later: recreate edges via FindEdge
for (auto [from, to] : node_pairs) {
    edges.push_back(facade.FindEdge(from, to));
}

After:

// Search returns both nodes and edges
auto unpacked_path = search(...);
weight = unpacked_path.weight;
unpacked_nodes = std::move(unpacked_path.nodes);
unpacked_edges = std::move(unpacked_path.edges);

// Use pre-computed edges directly
unpackPath(facade, unpacked_nodes, unpacked_edges, ...);

Original prompt

---

This section details on the original issue you should resolve

<issue_title>search functions should return unpacked nodes and edges</issue_title>
<issue_description>As a left-over from the MLD shortest path plugin implementation in two stub functions unpacked_edges array is ignored and later created from unpacked_nodes via facade.FindEdge.

To simplify interfaces and avoid unnecessary work the search functions should return unpacked nodes and edges.

EDIT: removed 5.8 milestone after inspecting the shortest path plugin code: "easy" but not desirable solution requires duplication of paths concatenation logic.</issue_description>

<agent_instructions>Check if this still holds true and devise a fix for the issue described</agent_instructions>

Comments on the Issue (you are @claude[agent] in this section)

• Fixes search functions should return unpacked nodes and edges #4001