panopus.libopus.path JVM system property: set to a full path to load a specific
libopus shared library instead of the OS default. Useful for bundling or testing
against a non-system build of libopus without needing OS environment variables.
When the library cannot be loaded, a descriptive IllegalStateException is thrown
with installation hints and the underlying OS error, instead of a bare
IllegalArgumentException: Cannot open library.
README "Custom library path" section restructured to document the new JVM system
property as the primary (recommended) approach, with OS-level env-var mechanisms
moved to a secondary option.