PET v0.1.5 — Fix target-aware dropped-prime exponents
Fix target-aware rewrite paths when removing a source prime with exponent greater than 1.
Previously, target-aware rewrite divided by the removed prime only once, so paths such as 18 -> 2, 50 -> 2, and 3718 -> 22 stopped early.
The path now applies unit DEC steps down to exponent 1 before applying DROP.
Validated with targeted CLI rewrite tests.