feat(server-mode): native-like folder browser, a developer kept to their own folder, no password minimum

- Folder browser (the Browse fallback for a remote browser): back/forward/up,
  a clickable breadcrumb that becomes a path field (Ctrl+L), Places (Home,
  the user's workspaces, recent picks), a filter, Name/Modified columns,
  Show hidden and New folder. A click selects; a double-click or Enter
  opens a folder or picks a file; Backspace goes up; typing jumps to a name.
- GET /api/lanes/browse: `hidden=1` (never the dot entries at the top of a
  non-admin's own folder), each entry's `mtime`, the answer's `home`.
- POST /api/lanes/browse/mkdir: one plain folder name inside an existing
  folder; a non-admin only in their own folder, none in server mode without
  one; under S3 a member's folder is made as the member.
- scope.ownFolder falls back to server.conf's USERS_ROOT under S3, so a
  settings file without AGENTHUB_USERS_ROOT no longer opens the host's home
  to every developer.
- Passwords: any non-empty password is accepted (no 8-character minimum).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/openapi-extra/auth.js

@@ -241,7 +241,7 @@ const paths = {
               required: ["username", "password", "currentPassword"],
               properties: {
                 username: { type: "string" },
-                password: { type: "string", minLength: 8 },
+                password: { type: "string", minLength: 1 },
                 role: {
                   type: "string",
                   enum: ["admin", "analyst", "developer"],
@@ -282,7 +282,7 @@ const paths = {
       operationId: "resetServerUserPassword",
       summary: "Admin: a new password for that user; every login of theirs ends",
       parameters: [idParam],
-      requestBody: changeBody({ password: { type: "string", minLength: 8 } }, ["password"]),
+      requestBody: changeBody({ password: { type: "string", minLength: 1 } }, ["password"]),
       responses: changeResponses,
     },
   },