Command::quit calls exit(0) from inside the library, silently killing the host process

[HugoFara]

quit[] calls exit(0) inside the library (Command.cpp:2967), so it kills any host process, including Python:

f = pyforefire.ForeFire()
try:
    f.execute("quit[]")   # process ends here
finally:
    print("never printed")

The host gets no exception, finally and atexit never run, buffered output is lost, and the exit status is 0, so a CI job reports success.

The error path at Command.cpp:1125 (// TODO supersafe mode ?) also calls quit(), so an internal error can do the same thing.

Fix in #181.

Suggested fix: quit releases the session and returns; the CLI in app/forefire/ decides whether to exit. Line 1125 should return an error instead. Related to #159.

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Drafted with Claude Opus 5, reviewed by a maintainer.