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>

docs/LANES.md

@@ -89,7 +89,7 @@ than behind a disclosure — a disclosure around a single field only hid it.
 
 A workspace has no AI Proxy of its own: each NEW session picks one. The **AI Proxy** select in the workspace home's prompt box lists the profiles saved in Settings › AI Proxy (9Router, OpenRouter, a self-hosted gateway) plus **Native** (the vendor's own API); it shows Native alone, disabled, when the session's AI tool cannot use a proxy (only Claude and Codex can), and it remembers the last pick (`agenthub.session.proxy`, falling back to the pre-rename `agenthub.session.router`). The start sends `proxy: "<name>"` (`router` is still accepted); a Claude pane then runs with `--settings=<data dir>/proxy-settings/<name>.json`, which outranks the workspace's own settings, and a Codex pane with `-p <name>` plus its key through tmux `-e`. So two sessions of one workspace can run on two proxies, a worktree session gets its proxy too, and switching never touches a running session. A resume goes back to the proxy its session last ran on (`dashboard_runs.proxy`). Editing a profile in Settings rewrites those files (a rotated key reaches live Claude sessions); deleting it removes them. Older builds wrote a workspace's proxy into its `.claude/settings.local.json`; every server start takes those eight keys back out. See `docs/API.md` § AI Proxy profiles.
 
-Both modes' path field has a **Browse** button next to it that opens the operating system's own folder picker (`POST /api/lanes/pick-path`). A browser cannot hand a web page an absolute path from its own dialog, so the SERVER opens the dialog on its desktop (zenity/kdialog on Linux, `osascript` on macOS, PowerShell on Windows) — which is your screen only when the browser runs on the same machine. A browser on another machine, or a server with no desktop or no zenity/kdialog, gets the small in-app folder browser instead (`GET /api/lanes/browse?path=<abs>`): click a subfolder to descend, ".." to go up, "Select this folder" to fill the path field; git repos are marked. The same button sits beside the workspace home's **Folder** field, Import history's folder, the project-memory folder, CLAUDE_HOME/CODEX_HOME and a remote source's SSH identity file (a file picker: its in-app fallback lists the folder's files too, and a click on a file picks it).
+Both modes' path field has a **Browse** button next to it that opens the operating system's own folder picker (`POST /api/lanes/pick-path`). A browser cannot hand a web page an absolute path from its own dialog, so the SERVER opens the dialog on its desktop (zenity/kdialog on Linux, `osascript` on macOS, PowerShell on Windows) — which is your screen only when the browser runs on the same machine. A browser on another machine, or a server with no desktop or no zenity/kdialog, gets the in-app folder browser instead (`GET /api/lanes/browse?path=<abs>`), laid out like a native picker: Back/Forward/Up, a clickable breadcrumb that becomes a path field (✎ or Ctrl+L), Places (Home, your workspaces, recent picks), a filter, Name/Modified columns (click to sort), **Show hidden**, and **New folder**. A click selects, a double-click or Enter opens (Backspace goes up, typing jumps to a name), and "Select this folder" fills the path field with the selected folder, else the one shown; git repos are marked. The same button sits beside the workspace home's **Folder** field, Import history's folder, the project-memory folder, CLAUDE_HOME/CODEX_HOME and a remote source's SSH identity file (a file picker: its in-app fallback lists the folder's files too, and a double-click on a file picks it).
 
 ## Workspace tool: Claude or Codex