fix: classify "No conversation found" as session_expired

Claude CLI returns "No conversation found with session ID: <id>"
when resuming an expired session. The existing error classifier
checks for "conversation not found" but misses the "no conversation
found" phrasing, so the session-expired recovery path (clear stale
binding, retry with fresh session) never fires.

This causes follow-up messages in CLI-backend conversations to fail
permanently instead of transparently creating a new session.

Added "no conversation found" to isCliSessionExpiredErrorMessage()
alongside the existing "conversation not found" pattern.

src/agents/pi-embedded-helpers.isbillingerrormessage.test.ts

@@ -648,6 +648,12 @@ describe("classifyFailoverReason", () => {
     expect(classifyFailoverReason("410 conversation expired")).toBe("session_expired");
   });
 
+  it("classifies 'No conversation found' from Claude CLI as session_expired", () => {
+    expect(classifyFailoverReason("No conversation found with session ID: abc123")).toBe(
+      "session_expired",
+    );
+  });
+
   it("keeps explicit billing and auth signals on 410 text", () => {
     expect(classifyFailoverReason("HTTP 410: invalid_api_key")).toBe("auth");
     expect(classifyFailoverReason("HTTP 410: authentication failed")).toBe("auth");

src/agents/pi-embedded-helpers/errors.ts

@@ -1109,6 +1109,7 @@ function isCliSessionExpiredErrorMessage(raw: string): boolean {
     lower.includes("session expired") ||
     lower.includes("session invalid") ||
     lower.includes("conversation not found") ||
+    lower.includes("no conversation found") ||
     lower.includes("conversation does not exist") ||
     lower.includes("conversation expired") ||
     lower.includes("conversation invalid") ||