Kill the surviving mutants in graph-projection #65

Large parts of the fragment, chain-folding and inverse (state machine, flowchart) logic are uncovered or survive, including the inverses' rejection branches. These are the most-affected files in @exadev/process-graph-projection on main's mutation run (https://github.com/ExaDev/process-graph/actions/runs/38170535483), with a few of the lines a surviving or uncovered mutant changes; the shard log and the uploaded HTML report have the full list.

packages/core/graph/projection/src/fragments.ts (75 survived, 84 without coverage):

• packages/core/graph/projection/src/fragments.ts:123:21 MethodExpression mutant, survived, on const branching = model.elements.filter(
• packages/core/graph/projection/src/fragments.ts:125:7 ConditionalExpression mutant, survived, on onPath.has(element.id) &&
• packages/core/graph/projection/src/fragments.ts:126:8 ConditionalExpression mutant, survived, on (element.kind === "decision" ||
• packages/core/graph/projection/src/fragments.ts:127:39 ConditionalExpression mutant, survived, on (element.kind === "pseudo" && element.role === "fork")),

packages/core/graph/projection/src/chains.ts (103 survived, 37 without coverage):

• packages/core/graph/projection/src/chains.ts:132:9 ConditionalExpression mutant, survived, on if (set.size >= enough) {
• packages/core/graph/projection/src/chains.ts:152:7 MethodExpression mutant, survived, on (outgoing.get(id) ?? [])
• packages/core/graph/projection/src/chains.ts:154:17 ArrowFunction mutant, survived, on .filter((target) => foldable.has(target)),
• packages/core/graph/projection/src/chains.ts:173:31 ConditionalExpression mutant, survived, on if (from !== undefined && to === undefined && accepted(transition.target)) {

packages/core/graph/projection/src/inverse-state-machine.ts (41 survived, 36 without coverage):

• packages/core/graph/projection/src/inverse-state-machine.ts:51:40 BlockStatement mutant, survived, on for (const state of original.states) {
• packages/core/graph/projection/src/inverse-state-machine.ts:52:9 ConditionalExpression mutant, survived, on if (!kept.has(state.id)) {
• packages/core/graph/projection/src/inverse-state-machine.ts:63:11 ConditionalExpression mutant, survived, on if (elements.has(state.id)) {
• packages/core/graph/projection/src/inverse-state-machine.ts:77:11 ConditionalExpression mutant, survived, on if (state.role !== "state") {

Kill them by asserting the behaviour, not by loosening or removing any existing assertion. Raise the package's breakThreshold from the new baseline once they are killed. Found while setting the break thresholds in #60.