fix: recover mobile and sync state after resume

Reconnect sync stream when native mobile app resumes
Materialize incomplete sessions with explicit recovery reasons
Add low-noise debug breadcrumb for scoped recovery

packages/ui/src/sync/event-reducer.ts

@@ -151,10 +151,23 @@ export type GlobalEventResult = {
   project: Project
 } | null
 
+export type SessionMaterializationReason =
+  | "missing-owning-message"
+  | "orphan-delta"
+  | "missing-delta-part"
+  | "empty-assistant-message"
+  | "child-session-idle"
+  | "child-session-discovered"
+  | "ensure-session-messages"
+  | "stream-reconnect"
+  | "transport-switch"
+  | "stale-status-resync"
+
 export type DirectoryEventResult = boolean | {
   changed: boolean
   materialization: {
     type: "incomplete-session-snapshot"
+    reason: SessionMaterializationReason
     sessionID?: string
     messageID: string
     partID?: string
@@ -356,7 +369,7 @@ export function applyDirectoryEvent(
         return missingOwningMessage
           ? {
             changed: true,
-            materialization: { type: "incomplete-session-snapshot", sessionID, messageID, partID: part.id },
+            materialization: { type: "incomplete-session-snapshot", reason: "missing-owning-message", sessionID, messageID, partID: part.id },
           }
           : true
       }
@@ -390,7 +403,7 @@ export function applyDirectoryEvent(
       return missingOwningMessage
         ? {
           changed: true,
-          materialization: { type: "incomplete-session-snapshot", sessionID, messageID, partID: part.id },
+          materialization: { type: "incomplete-session-snapshot", reason: "missing-owning-message", sessionID, messageID, partID: part.id },
         }
         : true
     }
@@ -426,7 +439,7 @@ export function applyDirectoryEvent(
         syncDebug.reducer.partDeltaNoParts(props.messageID, props.partID)
         return {
           changed: false,
-          materialization: { type: "incomplete-session-snapshot", sessionID: props.sessionID, messageID: props.messageID, partID: props.partID },
+          materialization: { type: "incomplete-session-snapshot", reason: "orphan-delta", sessionID: props.sessionID, messageID: props.messageID, partID: props.partID },
         }
       }
       const result = Binary.search(parts, props.partID, (p) => p.id)
@@ -434,7 +447,7 @@ export function applyDirectoryEvent(
         syncDebug.reducer.partDeltaNotFound(props.messageID, props.partID)
         return {
           changed: false,
-          materialization: { type: "incomplete-session-snapshot", sessionID: props.sessionID, messageID: props.messageID, partID: props.partID },
+          materialization: { type: "incomplete-session-snapshot", reason: "missing-delta-part", sessionID: props.sessionID, messageID: props.messageID, partID: props.partID },
         }
       }
       const existing = parts[result.index] as Record<string, unknown>