gbz-base: GBZ pangenome graph in SQLite

A prototype for storing a GBZ pangenome graph in an SQLite database, enabling interactive applications that need immediate access to parts of the graph without full in-memory loading. Currently at version 0.1.0-alpha.1, pre-stable. Key differentiators: uses SQLite for direct querying of graph slices, targets WASM for browser usage, and is intended to become an optional feature of GBWT-rs once stabilized. Released via npm as .wasm files, no JavaScript wrapper included.