PLAN.md: Move… is a folder picker; moves across filesystems copy then remove

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

PLAN.md

@@ -683,6 +683,30 @@ something long in one, switch away and back, refresh — it's all still there.
   - *Not done, on purpose:* no cap on the cache and no clear button (not asked; it only
     holds what was looked at); no tonemapping for HDR sources (a 10-bit HEVC frame comes out
     flat); no preview in the viewer for a video (it still says "binary, download it").
+- **Move… is a folder picker** — **shipped 2026-10-11** (v0.1.0-204, `MovePicker` in
+  `Files.tsx`, `internal/files/move.go`, `POST /api/files/move`). Asked for as: instead of
+  a path prompt, "an interactive file explorer, where I can go back/forward, etc and then
+  click some button, and it will move the file/folder to where I was". The picker opens in
+  the item's own folder and walks the machine the way the tab does — back and forward
+  through where it has been, up, breadcrumbs, a path box, folders only, `.hidden`
+  following the tab's toggle, **+ folder** to make the destination on the spot — and
+  **Move here** puts the item in the folder being looked at. It says why it can't when it
+  can't, with the button greyed: already here, a folder into itself, a name clash in that
+  folder (read from the listing before anything is tried). The row being moved shows in
+  its own folder, greyed. Rename stays a name prompt: it is a different question.
+  - **Across filesystems it copies, then removes.** `os.Rename` is EXDEV between
+    filesystems, and on `grid` every dataset is one — `/tank/media` to `/tank/files` was a
+    "invalid cross-device link" error before this, and the picker would have made that
+    move easy to attempt. `/api/files/move` renames when it can (204) and otherwise runs
+    `hamlab fs move` as a task (202 with the task; the tab shows its output and reloads
+    when it ends). The copy is built under a hidden name beside its destination
+    (`.<name>.hamlab-moving`), renamed into place once complete, and only then is the
+    original removed — a failure part-way removes the partial copy and leaves the original
+    as it was, and a cancel (SIGTERM to the helper) does the same. Modes, mtimes and
+    symlinks are kept; owners too when the backend is root. Devices, pipes and sockets are
+    refused outright rather than half-copied. Progress every 500 files or 512 MiB.
+    Verified on `grid` ext4 → ZFS with a tree holding a 0600 file, a symlink and an old
+    mtime, all intact on the other side.
 - **Docker read-only view** — `docker ps`/logs; dockhand stays the source of truth.
 - **Notifications** — push on service failure / SMART warning / UPS event.
 - **Terminal extras** — search, copy-mode, font/theme, split panes, upload via