feat: share clients — picker enhancements, unmount fixes, confirm default-y convention

- mountpoint picker: synthetic (as on server) candidate + n=new mkdir flow
- unmount-by-pick via findmnt enumeration with confirm
- cmd_unmount idle-persisted branch exit 0 → return 0 + actionable guidance
- all menu handlers normalized … || true
- confirm() rewrite: default-y on Enter, EOF fail-closed, case-insensitive
- latent compose "Y" bug fixed
- DEV.md convention doc for confirm semantics

DOC/DEV.md

@@ -72,7 +72,7 @@ Sourced by most scripts. Key functions:
 | `run cmd` | Executes command, respects `$DRY_RUN` |
 | `spawn "msg" cmd` | Animated braille spinner + elapsed time |
 | `timer_start` / `timer_stop` | Elapsed time tracking |
-| `confirm "prompt"` | y/N prompt with optional default |
+| `confirm "prompt" [default]` | y/n prompt; Enter accepts the default (`y` when omitted) |
 
 ---
 
@@ -428,6 +428,10 @@ pos-communication-<platform> send <value> [--markdown]   # exit 0 on delivery
 
 then listing it in `NOTIFY_PLATFORM`. Platform keys map to tool names via `notify_sender_name()` in `lib/notify.sh` — the telegram platform key stays `telegram` but its tool is `pos-communication-telegram-sender`. `pos-communication-telegram-sender` already follows this (`--markdown` is an alias for `--parse-mode markdown`). No changes to `lib/notify.sh` are needed for a new platform.
 
+### Confirmation prompts
+
+`confirm()` rule: Enter accepts the displayed default; destructive call sites pass explicit `'n'`.
+
 ### Idempotency
 
 Check before creating, use `>>` with grep guards, don't overwrite user configs.

DOC/howto/share.md

@@ -153,8 +153,14 @@ up — a down/unreachable NFS server can't break boot (with fstab it could).
 
 **Interactive menu:** run `pos share nfs client` with no args for a menu
 (mount / persist / unmount / unpersist / list). Mountpoints are offered from
-existing mount-layout candidates with manual entry as fallback; unmount and
-unpersist tolerate already-absent targets instead of erroring.
+existing mount-layout candidates with manual entry as fallback — the picker
+also accepts the server-side export path as a "(as on server)" pick when it
+differs from your local layout, and `n=new` creates a fresh directory in
+place (y/N confirmed; a failure just returns to the picker). Unmount lists
+the active NFS mounts as `<mountpoint> ← <source>` picks and asks for
+confirmation before unmounting (with a typed fallback when nothing is
+mounted); unmount and unpersist tolerate already-absent targets instead of
+erroring.
 
 **Troubleshooting:**
 - "mount.nfs not found" → `nfs-common` isn't installed; `sudo apt install nfs-common`
@@ -285,7 +291,13 @@ fstab it could). `enable --now` arms the automount immediately.
 (enumerate / mount / persist / unmount / unpersist / list). Enter the server,
 an empty user tries guest enumeration first (with an auth retry on denial),
 then shares and mountpoints are offered as pickers with manual fallback —
-the account you authenticated with is reused for the mount.
+the account you authenticated with is reused for the mount. The mountpoint
+picker accepts `n=new` to create a fresh directory in place (y/N confirmed;
+a failure just returns to the picker); when the server is this machine, its
+underlying share directory is offered as a "(as on server)" pick too.
+Unmount lists the active CIFS mounts as `<mountpoint> ← <source>` picks and
+asks for confirmation before unmounting (typed fallback when nothing is
+mounted).
 
 ---