Deletion

Deleting a word from a trie:

1. Walk to the word (return early if not found).
2. Unset is_word on the leaf.
3. Walk back up; for each node, if it has no children AND is not a word, delete it.

The recursion bubbles up "should_prune" booleans. Each node decides whether to delete the child based on whether the child is now useless (no descendants, not a word).

Edge cases:

• Word not in trie: no-op.
• Other words share a prefix: don't delete those nodes.