v0.3.0

Research-driven generative model families + costmap conditioning.

A deep literature/OSS survey found no open-source flow-matching / diffusion / consistency local planner for ROS 2 Nav2 ground robots. This release adds all three behind the TrajectoryModel ONNX seam:

• Flow matching (single/few-step), diffusion (cosine DDPM + DDIM), consistency (one-step distillation). Each exports a single self-contained ONNX file matching the [1,4] -> [1,K,H,3] backend contract; a trained flow model runs in the real C++ OnnxTrajectoryModel.
• Costmap+goal conditioning end to end (the surveyed gap): optional egocentric costmap patch through ModelContext → OnnxTrajectoryModel auto-detected costmap input → controller costmap_patch_size (default off, backward compatible). CostmapFlowPlanner / CostmapDiffusionPlanner / CostmapConsistencyPlanner train+export two-input ONNX.
• README hero GIF from the real pipeline; GPU/headless Gazebo notes.

Verified on ROS 2 Jazzy (build + gtest + pytest + ament lints). See CHANGELOG.md. Not a safety-certified product; see docs/safety.md.