feat: support multiple workspace roots (#584)

cli/src/utils/workspaceRoot.ts

@@ -1,17 +1,22 @@
 import { isAbsolute } from 'node:path'
 
 /**
- * Resolves the runner's workspace root — the directory tree the runner is
+ * Resolves the runner's workspace roots — the directory trees the runner is
  * allowed to browse and spawn sessions in. Returns `undefined` when the
  * user hasn't explicitly opted in; in that case the runner behaves like
- * the legacy hapi (no scoping, no /browse feature surfaced in the web UI).
+ * legacy hapi (no scoping, no /browse feature surfaced in the web UI).
  *
  * The only signal is the `explicit` argument — typically the resolved
- * `--workspace-root` flag. Non-absolute values are ignored.
+ * `--workspace-root` flag values. Non-absolute values are ignored.
  */
-export function resolveWorkspaceRoot(explicit?: string): string | undefined {
-    if (explicit && isAbsolute(explicit)) {
-        return explicit
+export function resolveWorkspaceRoots(explicit?: string[]): string[] | undefined {
+    if (!explicit?.length) {
+        return undefined
     }
-    return undefined
+
+    const uniqueRoots = Array.from(
+        new Set(explicit.filter((path): path is string => typeof path === 'string' && isAbsolute(path)))
+    )
+
+    return uniqueRoots.length > 0 ? uniqueRoots : undefined
 }