Without output_qasm, pareto-incremental still writes pareto_front/ and pareto_front.pdf #112

docs/reference.md:92 says:

Without output_qasm, no files are written: the circuit and the last formula go to a temporary directory that is removed when synthesis() returns.

The synthesis() docstring (src/synth.py:776) says the same ("None writes no files"). For mode="pareto-incremental" this isn't true. Every point of the front still goes to pareto_front/ and the plot to pareto_front.pdf, both in the working directory (src/pareto.py:116 and src/pareto.py:135-138).

Minimal example (in an empty directory, with yices2 configured):

import sys
sys.path.insert(0, "/path/to/milq/src")
from synth import Synthesizer

# no output_qasm: per the docs, no files should be written
Synthesizer().synthesis(qasm_file="/path/to/milq/benchmarks/ghz/2.qasm", vectors="zero", solving="smt",
                        solver="yices2", mode="pareto-incremental", pareto_timeout=60, max_depth=2)

Afterwards the directory contains:

pareto_front.pdf
pareto_front/pareto_2_2_2.000_1.qasm
pareto_front/pareto_2_2_2.000_2.qasm

docs/usage.md already mentions these files, and the behaviour predates the logging rewrite (#94), which added the sentence. There are two ways to fix it:

1. Docs only: add an exception for pareto-incremental to the reference and the docstring.
2. Code: without output_qasm, put pareto_front/ and the plot in the temporary directory too, so the sentence becomes true.

Found on master e5a5216.