[Karinon]

Summary

Every read method on NetCDF4 was implemented twice: once for the main thread and once for the Web Worker used by fromBlobLazy and fromUrl. The two copies could drift apart, and the worker's copy was untested.

All operations are now defined once, in the new src/operations.ts. Both paths run the same code, and each public method is a single call.

Because the tests run these operations on the main thread, they now also cover what the worker executes. Only the message passing and file mounting inside the worker still need a browser to test.

Small behavior changes

• On the worker path, getDimIDs() and getVarIDs() now return an Int32Array, as the main thread already did.
• Open and close errors are worded the same on both paths.
• Calling a method before the dataset is initialized now gives a clear error instead of a TypeError.