- Create `panda/src/navmesh` module structure.- Implement `NavMeshSettings` class for configuration.- Create skeleton `NavMeshBuilder`, `NavMesh`, and `NavPath` classes.- Register module in CMake build system.- Update architecture and progress documentation.

- Implement core NavMesh module skeleton and configuration (NavMeshSettings, NavMeshBuilder, NavMesh, NavPath).- Register module in CMake build system.- Establish error handling via `navmesh_cat`.- Create unit test infrastructure in `tests/navmesh/`.- Complete all tasks in Section 2 of navmesh-tasks.md.

This commit introduces the Recast and Detour navigation libraries as a third-party dependency in panda/src/navmesh/thirdparty. These libraries provide the core navigation mesh generation and pathfinding capabilities.

- Adds panda/src/navmesh to the build system in panda/CMakeLists.txt.- Creates panda/src/navmesh/CMakeLists.txt to configure the new module and link Recast/Detour.- Implements config_navmesh to handle configuration variables for navmesh generation (cell size, agent radius, etc.).

- NavMeshSettings: Encapsulates generation parameters.- NavMeshBuilder: Handles geometry extraction from the scene graph and generates the navigation mesh using Recast.- NavMeshPoly: Wrapper around Detour mesh data, providing pathfinding queries.- NavPath: Represents the result of a pathfinding query.

- Updates PathFind to accept a NavMeshPoly object.- Modifies path_find to delegate to the new NavMesh system when available.- Updates CMakeLists.txt to link against the new navmesh module.

- Adds basic tests for NavMeshBuilder and settings validation.- Ensures the module can be imported and basic operations perform as expected.