blueterra 0.1.0

• Initial development version.
• Added raster input, validation, preparation, terrain metrics, process groups, transects, isobath corridors, summaries, modeling helpers, plotting helpers, synthetic example data, tests, README, and vignettes.
• Added reduced real bathymetry examples from the southwest Puerto Rico shelf margin near La Parguera, Puerto Rico, plus sampling rectangles.
• Improved hillshade-supported terrain maps, site-location documentation, and scientific examples for README, vignettes, and visual proof.
• Added surface-oriented transect defaults, richer cross-section and PCA plots, citation metadata, and custom metric/process-group extension helpers.