terralink 1.8.0

Aligned the R package release version with the current TerraLink 1.8 QGIS plugin baseline.
Updated QGIS-facing helper scripts and parity references to target TerraLink_v1_8.

terralink 1.7.0

Harmonized the R package public strategy surface with the current plugin: most_connected_networks, largest_single_network, and landscape_fluidity.
Added graph-based habitat availability and landscape fluidity selectors for raster and vector workflows, plus expanded pre/post connectivity reporting.
Improved vector most_connected_networks selection to stay closer to TerraLink 1.7 QGIS results on the packaged parity fixture.
Added packaged synthetic raster/vector parity fixtures and an synthetic parity fixture set validated against QGIS.
Expanded README/vignette guidance with optimization-mode selection, scenario-comparison advice, and raster-vs-vector interpretation notes taken from the TerraLink 1.8 QGIS documentation.
Added methods references in DESCRIPTION and removed the interactive wrapper from terralink_raster() examples for CRAN submission readiness.

Added an explicit sf availability check in inst/scripts/run_vector.R before calling sf::st_read().
Reduced terralink_raster() example workload to stay below CRAN example timing thresholds on slower builders.
Added packaged sample data (inst/extdata) plus terralink_sample_data() for copy/paste runnable examples.
Updated vignette, README, and example scripts to use packaged sample files.
Aligned non-debug behavior with TerraLink 1.5.3 strategy/selector updates: most_connectivity defaults, enhanced overlap/distance guards, raster corridor assignment modes, and vector local efficiency scoring.