Checkpoint: The Ownership Seam

The task

Implement WF (see the challenge): a word-frequency table that strdups its keys, counts occurrences, hands out lookups into its own storage, and destroys everything it owns. This is the module's whole lesson in one structure: hashing, chaining, and the ownership seam — the table owns its keys, the tests verify the copies are distinct, and destroy frees every node and every key exactly once.

Passing this proves you can ship a generic container whose ownership policy is explicit and whose cleanup is provable — the bar every real library must clear.

Next module: the preprocessor — macros as a language over the language.