enforce convo-present invariant in snapshot instead of guarding in isConvoActive

the active convo states declare `convo` as non-optional, but a lifecycle
event (background/suspend) can move the machine into an active status before
setup() populates this.convo. generateSnapshot papered over this with
`this.convo!`, so isConvoActive trusted the status alone and downstream
consumers crashed dereferencing an undefined convo.

instead of guarding at the isConvoActive call site, make the invalid state
unrepresentable: generateSnapshot now reports Initializing whenever an active
status has no convo yet, which lets us drop all four non-null assertions. the
compiler now enforces that an active snapshot always carries a convo, so the
isConvoActive guard added earlier is reverted as redundant.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/state/messages/convo/agent.ts

@@ -237,22 +237,40 @@ export class Convo {
       removeReaction: undefined,
     }
 
+    /*
+     * Captured as a local so the `if (convo)` narrowing below survives the
+     * `this.getItems()` call - TS discards narrowing on mutable `this` members
+     * after a method call, but not on a const.
+     */
+    const convo = this.convo
+
+    /*
+     * A lifecycle event (e.g. `Background` or `Suspend`) can move us into an
+     * active status before `setup()` has resolved and populated `convo`. The
+     * active states declare `convo` as non-optional, so we can't build one
+     * without it - fall back to reporting `Initializing` until the convo lands.
+     * This keeps the snapshot's type and runtime in agreement, so consumers can
+     * trust that an active status always has a `convo`.
+     */
+    const stillInitializing = (): ConvoState => ({
+      status: ConvoStatus.Initializing,
+      items: [],
+      convo,
+      error: undefined,
+      ...shared,
+      ...emptyMethods,
+    })
+
     switch (this.status) {
       case ConvoStatus.Initializing: {
-        return {
-          status: ConvoStatus.Initializing,
-          items: [],
-          convo: this.convo,
-          error: undefined,
-          ...shared,
-          ...emptyMethods,
-        }
+        return stillInitializing()
       }
       case ConvoStatus.Disabled: {
+        if (!convo) return stillInitializing()
         return {
-          status: this.status,
+          status: ConvoStatus.Disabled,
           items: this.getItems(),
-          convo: this.convo!,
+          convo,
           relatedProfiles: this.relatedProfiles,
           error: undefined,
           ...shared,
@@ -260,10 +278,11 @@ export class Convo {
         }
       }
       case ConvoStatus.Suspended: {
+        if (!convo) return stillInitializing()
         return {
-          status: this.status,
+          status: ConvoStatus.Suspended,
           items: this.getItems(),
-          convo: this.convo!,
+          convo,
           relatedProfiles: this.relatedProfiles,
           error: undefined,
           ...shared,
@@ -271,10 +290,11 @@ export class Convo {
         }
       }
       case ConvoStatus.Backgrounded: {
+        if (!convo) return stillInitializing()
         return {
-          status: this.status,
+          status: ConvoStatus.Backgrounded,
           items: this.getItems(),
-          convo: this.convo!,
+          convo,
           relatedProfiles: this.relatedProfiles,
           error: undefined,
           ...shared,
@@ -282,10 +302,11 @@ export class Convo {
         }
       }
       case ConvoStatus.Ready: {
+        if (!convo) return stillInitializing()
         return {
-          status: this.status,
+          status: ConvoStatus.Ready,
           items: this.getItems(),
-          convo: this.convo!,
+          convo,
           relatedProfiles: this.relatedProfiles,
           error: undefined,
           ...shared,

src/state/messages/convo/util.ts

@@ -21,19 +21,12 @@ export type ActiveConvoStates =
  * Checks if a `Convo` has a `status` that is "active", meaning the chat is
  * loaded and ready to be used, or its in a suspended or background state, and
  * ready for resumption.
- *
- * The `convo` object must also be present. The status can transition into an
- * active state before the convo has finished loading (e.g. `Initializing`
- * receives a `Background` event before `setup()` resolves), and every
- * `ActiveConvoStates` member declares `convo` as non-optional, so we guard
- * against that race here rather than crashing downstream consumers.
  */
 export function isConvoActive(convo: ConvoState): convo is ActiveConvoStates {
   return (
-    convo.convo !== undefined &&
-    (convo.status === ConvoStatus.Ready ||
-      convo.status === ConvoStatus.Backgrounded ||
-      convo.status === ConvoStatus.Suspended ||
-      convo.status === ConvoStatus.Disabled)
+    convo.status === ConvoStatus.Ready ||
+    convo.status === ConvoStatus.Backgrounded ||
+    convo.status === ConvoStatus.Suspended ||
+    convo.status === ConvoStatus.Disabled
   )
 }