fix: serialize model/permissions/restoredAt fields in metadata read/write

The session-manager already writes model, permissions, and restoredAt to
metadata during spawn() and restore(), but writeMetadata() and
readMetadata() silently dropped these fields during serialization.

This caused session.metadata?.["model"] and session.metadata?.["permissions"]
to always be undefined when reading back from disk, preventing restored
sessions from preserving their original agent configuration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/metadata.ts

@@ -99,6 +99,9 @@ export function readMetadata(dataDir: string, sessionId: SessionId): SessionMeta
     project: raw["project"],
     createdAt: raw["createdAt"],
     runtimeHandle: raw["runtimeHandle"],
+    permissions: raw["permissions"],
+    model: raw["model"],
+    restoredAt: raw["restoredAt"],
     dashboardPort: raw["dashboardPort"] ? Number(raw["dashboardPort"]) : undefined,
     terminalWsPort: raw["terminalWsPort"] ? Number(raw["terminalWsPort"]) : undefined,
     directTerminalWsPort: raw["directTerminalWsPort"] ? Number(raw["directTerminalWsPort"]) : undefined,
@@ -141,6 +144,9 @@ export function writeMetadata(
   if (metadata.project) data["project"] = metadata.project;
   if (metadata.createdAt) data["createdAt"] = metadata.createdAt;
   if (metadata.runtimeHandle) data["runtimeHandle"] = metadata.runtimeHandle;
+  if (metadata.permissions) data["permissions"] = metadata.permissions;
+  if (metadata.model) data["model"] = metadata.model;
+  if (metadata.restoredAt) data["restoredAt"] = metadata.restoredAt;
   if (metadata.dashboardPort !== undefined)
     data["dashboardPort"] = String(metadata.dashboardPort);
   if (metadata.terminalWsPort !== undefined)

packages/core/src/types.ts

@@ -965,6 +965,8 @@ export interface SessionMetadata {
   project?: string;
   createdAt?: string;
   runtimeHandle?: string;
+  permissions?: string;
+  model?: string;
   restoredAt?: string;
   dashboardPort?: number;
   terminalWsPort?: number;