Is there a technical name for this kind of wordplay?

terminology puns

Wikipedia suggests that they are blend words.

There are many types of blends, based on how they are formed. Algeo, a linguist, proposed dividing blends into three groups:
1. Phonemic Overlap: a syllable or part of a syllable is shared between two words
2. Clipping: the shortening of two words and then compounding them
3. Phonemic Overlap and Clipping: shortening of two words to a shared syllable and then compounding

The first group applies to the examples you have listed.

Pop-culture note: Wheel of Fortune calls puzzles with this style of answer "Before and After" puzzles. The answers are not blended into a single word as you have suggested, but the wit and construction are the same as your usage.

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