test(goal-session): pin the unsettled-attempt yield with a real failure path

The drive-pass guard for an unsettled attempt was wrongly annotated
unreachable after admission joined the running interval. It is reachable:
a contained turn-close failure (pre-commit turn/end rejection) reaches
idle with the attempt's turn open and no terminal reason, and the idle
drive pass must yield to that attempt instead of misreading the absent
reason as settled. Replace the ignore with a test driving exactly that
path; the guard's comment now names the real producer.

packages/goal/goal-session/src/index.ts

@@ -176,10 +176,9 @@ export function apply(ctx: Context): void {
 
     const attempt = state.attempt
     if (attempt !== undefined) {
-      // Prompt admission joined the loop's running interval, so a drive pass
-      // (which requires idle) can no longer observe an unsettled attempt;
-      // kept as a backstop against a future trigger inside the interval.
-      /* v8 ignore next -- unreachable yield, see above */
+      // Still unsettled: a contained turn-close failure reaches idle with the
+      // attempt's turn open in the log and no terminal reason recorded, so
+      // the drive pass must yield rather than misread it as settled.
       if (attempt.reason === undefined) return
       state.attempt = undefined
       const turn = attempt.turn