remove chance of removing mutations from other trees

[anoobindisguise]

Summary

Balance "mutations don't remove mutations from other trees unless they would conflict"

Purpose of change

Fixes #60126
TLDR: There are a lot of barriers in place already to hybridizing mutation trees in place already and there doesn't need to be an additional 25% chance per mutation out of the tree of mutation line you are currently mutating to be removed automatically.

Describe the solution

Remove entirely. Leave standard mutation conflicts, instability and mutation costliness as barriers to hybridizing the tree.

Describe alternatives you've considered

none tbh. I feel strongly about this

Testing

1. Spawned new character.
2. Injected with Feline Mutagen.
3. Turned partially into a cat with no issues.
4. Injected with Cephalopod Mutagen.
5. Started to turn into a squid. Didn't lose any of my Feline mutations except when Cephalopod wanted to override them (my Retractable Claws turned into regular claws as part of gaining tentacle arms, my fur turned into rough skin so it could become a shell, but my cat ears didn't ever go away because Cephalopod doesn't counter those)
6. Injected myself with Purifier and purified back to baseline. No errors or crashes.

Additional context

[bombasticSlacks]

I think that this is reasonable.

HOWEVER I would ask the question does this exist so that human mutagen clears your mutations. Like without this does purifier break.

[anoobindisguise]

I think that this is reasonable.

HOWEVER I would ask the question does this exist so that human mutagen clears your mutations. Like without this does purifier break.

I believe purifier should still work. It tries to mutate you towards specific hidden mutations that remove your existing ones. And it worked before the 1/4 chance to remove cross-tree muts was added, as there was a time where that wasn't the case under the new system. However it definitely bears testing first.

[actually-a-cat]

        } else {
            // Remove existing mutations that don't fit into our category
            if( !downgrades.empty() ) {
                size_t roll = rng( 0, downgrades.size() + 4 );
                if( roll < downgrades.size() ) {
                    remove_mutation( downgrades[roll] );
                    return;
                }
            }

This bit also needs to go.

[anoobindisguise]

        } else {
            // Remove existing mutations that don't fit into our category
            if( !downgrades.empty() ) {
                size_t roll = rng( 0, downgrades.size() + 4 );
                if( roll < downgrades.size() ) {
                    remove_mutation( downgrades[roll] );
                    return;
                }
            }

This bit also needs to go.

good catch, thank you.

[anoobindisguise]

earlier today I did test this in game and left my notes in the testing section of the PR, it's functional and I didn't find any errors or weirdness.