feat: menu doors for media-sync/backup/compose/schedule/vbox/download; firewall menu → stderr+/dev/tty mechanics

DOC/DEV.md

@@ -31,7 +31,7 @@ Each phase is independent and runs only if the corresponding script exists.
 |-----------|---------|-------------|
 | `bin/` | Daily-use CLI tools and wrappers | `/usr/local/bin/` |
 | `apps/<category>/` | Optional desktop app installers | run on demand |
-| `lib/` | Shared libraries: `common.sh` (helpers), `flags.sh` (feature flags), `notify.sh` (multi-platform alerting), `entertainment-lib.sh` (entertainment scheduling + last-run state), `entertainment-plugin-lib.sh` (message-safe plugin helpers), `scheduler-lib.sh` (system scheduler), `user-timers-lib.sh` (shared systemd user timer machinery), `config-ui.sh` (interactive config UI) | sourced at build time |
+| `lib/` | Shared libraries: `common.sh` (helpers), `flags.sh` (feature flags), `notify.sh` (multi-platform alerting), `entertainment-lib.sh` (entertainment scheduling + last-run state), `entertainment-plugin-lib.sh` (message-safe plugin helpers), `scheduler-lib.sh` (system scheduler), `user-timers-lib.sh` (shared systemd user timer machinery), `config-ui.sh` (interactive config UI), `menu-lib.sh` (category-neutral menu primitives: guard/looping menu/filter picker/prompt), `share-lib.sh` (share-suite domain probes/listings + compat shims to menu-lib) | sourced at build time |
 | `config/` | Gitignored user config files | `~/.config/<app>/` (via postinstall) |
 | `entertainment/` | Public-API plugins for the entertainment module | `/usr/local/bin` (via install.sh Phase 2) |
 | `compose/` | ScaleTail templates (git submodule) | `/usr/local/share/linux_post_install/scale-tail` |
@@ -193,7 +193,7 @@ make lint                     # convention gate (scripts/lint-conventions.sh)
 
 `make check` only proves syntax, exec bits, doc sync and dispatch — not behaviour. For tools that need `sudo`, systemd, or binaries absent from the dev box (samba, usbsrv, …), test them end-to-end with two patterns:
 
-- **Env-overridable paths.** Anything that touches a system config location gets an env override whose default is the real path — the seam that lets the tool be exercised against temp files. Precedents: `FLAGS_DIR` (`lib/flags.sh`), `SMB_CONF` (`bin/pos-share-smb-server`, default `/etc/samba/smb.conf`), `SMB_CREDS_DIR`/`UNIT_DIR` (`bin/pos-share-smb-client`), `USER_SYSTEMD_DIR` (`bin/pos-network-download`, `bin/pos-communication-{telegram,matrix}-listener`, `lib/scheduler-lib.sh` — write it as `${USER_SYSTEMD_DIR:-${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user}`), the scheduler's `SCHEDULE_DIR`/`SCHEDULE_STATE_DIR`/`SCHEDULE_LOG_DIR`/`SCHED_LEGACY_ENV` (`lib/scheduler-lib.sh`), and the USB layer shared by `pos system backup` + `pos media sync`: `USB_MOUNT_BASE` (default `/media`, keeps `BACKUP_MOUNT_BASE` as an alias) and `USB_BYID` (default `/dev/disk/by-id`, keeps `BACKUP_USB_BYID` as an alias) — both guarded as `VAR="${VAR:-${BACKUP_…:-default}}"` in `lib/usb-lib.sh` so existing config lines keep working. Pick a short tool-specific name and don't advertise it in `usage()` — it's a test seam, not user-facing. **Gotcha (session-learned):** a `VAR="${XDG…:-…}"` without the leading `VAR:-` *overrides* the seam — the stub run then silently writes to the real `$HOME` path and every assertion passes while the bug hides. The override must be written first, then tested with `VAR=/tmp/x …` and a check that the real path is untouched.
+- **Env-overridable paths.** Anything that touches a system config location gets an env override whose default is the real path — the seam that lets the tool be exercised against temp files. Precedents: `FLAGS_DIR` (`lib/flags.sh`), `SMB_CONF` (`bin/pos-share-smb-server`, default `/etc/samba/smb.conf`), `EXPORTS_FILE` (`bin/pos-share-nfs-server`, default `/etc/exports`), `SMB_CREDS_DIR`/`UNIT_DIR` (`bin/pos-share-smb-client`, and `UNIT_DIR` again in `bin/pos-share-nfs-client`), `USER_SYSTEMD_DIR` (`bin/pos-network-download`, `bin/pos-communication-{telegram,matrix}-listener`, `lib/scheduler-lib.sh` — write it as `${USER_SYSTEMD_DIR:-${XDG_CONFIG_HOME:-$HOME/.config}/systemd/user}`), the scheduler's `SCHEDULE_DIR`/`SCHEDULE_STATE_DIR`/`SCHEDULE_LOG_DIR`/`SCHED_LEGACY_ENV` (`lib/scheduler-lib.sh`), and the USB layer shared by `pos system backup` + `pos media sync`: `USB_MOUNT_BASE` (default `/media`, keeps `BACKUP_MOUNT_BASE` as an alias) and `USB_BYID` (default `/dev/disk/by-id`, keeps `BACKUP_USB_BYID` as an alias) — both guarded as `VAR="${VAR:-${BACKUP_…:-default}}"` in `lib/usb-lib.sh` so existing config lines keep working. Pick a short tool-specific name and don't advertise it in `usage()` — it's a test seam, not user-facing. **Gotcha (session-learned):** a `VAR="${XDG…:-…}"` without the leading `VAR:-` *overrides* the seam — the stub run then silently writes to the real `$HOME` path and every assertion passes while the bug hides. The override must be written first, then tested with `VAR=/tmp/x …` and a check that the real path is untouched.
 - **Stub PATH.** Create a temp dir with fake binaries, then run the tool with `PATH="$stubs:$PATH"`: fake `sudo` → `exec "$@"`; fake `systemctl`/`smbcontrol`/`mount.cifs` → echo their args; fake `testparm` → `cat` the file back (so validation passes); fake `systemd-escape` → print a fixed name. Assert on output **and** exit codes — happy path plus each failure path (`err` sets rc=1).
 - **Interactive prompts** (`read … </dev/tty`): drive them with a PTY — `printf 'answer\n' | script -qec "cmd" /dev/null` — then assert the side effect (e.g. the chmod-600 creds file lands with the right mode).