feat: add CLI backend fallback

src/agents/cli-session.ts

@@ -0,0 +1,33 @@
+import type { SessionEntry } from "../config/sessions.js";
+import { normalizeProviderId } from "./model-selection.js";
+
+export function getCliSessionId(
+  entry: SessionEntry | undefined,
+  provider: string,
+): string | undefined {
+  if (!entry) return undefined;
+  const normalized = normalizeProviderId(provider);
+  const fromMap = entry.cliSessionIds?.[normalized];
+  if (fromMap?.trim()) return fromMap.trim();
+  if (normalized === "claude-cli") {
+    const legacy = entry.claudeCliSessionId?.trim();
+    if (legacy) return legacy;
+  }
+  return undefined;
+}
+
+export function setCliSessionId(
+  entry: SessionEntry,
+  provider: string,
+  sessionId: string,
+): void {
+  const normalized = normalizeProviderId(provider);
+  const trimmed = sessionId.trim();
+  if (!trimmed) return;
+  const existing = entry.cliSessionIds ?? {};
+  entry.cliSessionIds = { ...existing };
+  entry.cliSessionIds[normalized] = trimmed;
+  if (normalized === "claude-cli") {
+    entry.claudeCliSessionId = trimmed;
+  }
+}