docs(swingset-liveslots): Restore tildot example that might be important

packages/swingset-liveslots/src/vpid-tracking.md

@@ -2,7 +2,7 @@
 
 Kernels and vats communicate about promises by referring to their VPIDs: vat(-centric) promise IDs. These are strings like `p+12` and `p-23`. Like VOIDs (object IDs), the plus/minus sign indicates which side of the boundary allocated the number (`p+12` and `o+12` are allocated by the vat, `p-13` and `o-13` are allocated by the kernel). But where the object ID sign also indicates which side "owns" the object (i.e. where the behavior lives), the promise ID sign is generally irrelevant.
 
-Instead, we care about which side holds the resolution authority for a promise (referred to as being its **decider**). This is not indicated by the VPID sign, and in fact is not necessarily static. Liveslots does not currently have any mechanism to allow one promise to be forwarded to another, but if it acquires this some day, then the decider of a promise could shift from kernel to vat to kernel again before it finally gets resolved. And there *are* sequences that allow a vat to receive a reference to a promise in method arguments before receiving a message for which that same VPID identifies the result promise (e.g., `{ promise: p1, resolve: resolveP1 } = makePromiseKit(); p2 = E(p1).push('queued'); await E(observer).push(p2); resolveP1(observer);` with an observer whose `push` returns a prompt response). In such cases, the decider is initially the kernel but later becomes the receiving vat.
+Instead, we care about which side holds the resolution authority for a promise (referred to as being its **decider**). This is not indicated by the VPID sign, and in fact is not necessarily static. Liveslots does not currently have any mechanism to allow one promise to be forwarded to another, but if it acquires this some day, then the decider of a promise could shift from kernel to vat to kernel again before it finally gets resolved. And there *are* sequences that allow a vat to receive a reference to a promise in method arguments before receiving a message whose result promise uses that same VPID (e.g., `p1 = p2~.foo(); x~.bar(p1)`, then someone resolves `p2` to `x`. Consider also tildot-free code like `{ promise: p1, resolve: resolveP1 } = makePromiseKit(); p2 = E(p1).push('queued'); await E(observer).push(p2); resolveP1(observer);` with an observer whose `push` returns a prompt response). In such cases, the decider is initially the kernel but that authority is transferred to a vat later.
 
 Each Promise starts out in the "unresolved" state, then later transitions irrevocably to the "resolved" state. Liveslots frequently (but not always) pays attention to this transition by calling `then` to attach fulfillment/rejection settlement callbacks. To handle resolution cycles, liveslots remembers the resolution of old promises in a `WeakMap` for as long as the Promise exists. Consequently, for liveslots' purposes, every Promise is either resolved (a callback has fired and liveslots remembers the settlement), or unresolved (liveslots has not yet seen a resolution that settles it).