SeaExplorerIO.jl: pure-Julia readers for Alseamar SeaExplorer glider log files

SeaExplorerIO.jl reads Alseamar SeaExplorer glider log files — navigation (gli) and payload (pld1, legato, ...) streams, both segment-numbered logs from the glider computer and concatenated GLIMPSE-server CSV exports — into a uniform column table. It is deliberately the file layer only: stream discovery, transfer-gap detection, robust parsing (corrupt files skipped loudly, sentinel fills handled), timestamp and NMEA-coordinate normalization, and multi-download-route merging with exact-timestamp deduplication. It serves as the shared loading layer for GliderADCP.jl and GliderTurbulence.jl.