fix: Add SessionInfoUpdate to SessionUpdate type in helpers (#61)

* fix: Add SessionInfoUpdate to ToolCallContentVariant

* fix: add miss import

Signed-off-by: Chojan Shang <psiace@apache.org>

---------

Signed-off-by: Chojan Shang <psiace@apache.org>
Co-authored-by: Chojan Shang <psiace@apache.org>

Author: observerw

src/acp/helpers.py

@@ -20,6 +20,7 @@
     PlanEntryPriority,
     PlanEntryStatus,
     ResourceContentBlock,
+    SessionInfoUpdate,
     SessionNotification,
     TerminalToolCallContent,
     TextContentBlock,
@@ -45,6 +46,7 @@
     | UserMessageChunk
     | ToolCallStart
     | ToolCallProgress
+    | SessionInfoUpdate
 )
 
 ToolCallContentVariant = ContentToolCallContent | FileEditToolCallContent | TerminalToolCallContent