chore(release): prep 0.1.65-beta.4 changelog

Update CHANGELOG.md in place per beta policy and add a compat note on the
`sub_agent.actions` field flagging it as drop-on-cleanup once clients
<= 0.1.65-beta.3 are out of the field.

packages/server/src/shared/messages.ts

@@ -415,6 +415,9 @@ const ToolCallDetailPayloadSchema: z.ZodType<ToolCallDetail, z.ZodTypeDef, unkno
       description: z.string().optional(),
       childSessionId: z.string().optional(),
       log: z.string(),
+      // Compat cruft for clients <= 0.1.65-beta.3 that required this field. Producers still
+      // emit `[]`; nothing reads it. Drop the field (and the `[]` emissions) once those
+      // clients are no longer in the field.
       actions: z
         .array(
           z.object({