docs: CR-6 — Hinweis auf installierten Befehl sporel-mapper

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -12,6 +12,8 @@ node bin/mapper.js <subcommand> [args...]
 
 Requires Node ≥18. Zero runtime dependencies.
 
+The `bin` entry in `package.json` exposes the command as `sporel-mapper`, so once globally installed or symlinked into `$PATH` you can invoke `sporel-mapper <subcommand>` directly in place of `node bin/mapper.js <subcommand>`. The examples below use the `node bin/mapper.js` form.
+
 ## Subcommands
 
 ### `encode <atlas_idx> <tile_id> [rotation]`