A copy into a picked folder says where it went, and Show takes you there

The last acceptance criterion M16 had left open. After Copy to..., the snackbar reads 'Copied to AADst' with a Show button; after a move to a picked folder it keeps the undoable message instead, because the sources are gone and Show would lead nowhere.

Two things needed care rather than a string. The action button was hard-wired to undo() - the label was a parameter beside it, which let the two disagree - so UiMessage now carries a MessageAction, and the label follows from it: Undo for an undo, Show for a jump. And a message cannot name a folder from the path alone: a volume root has no name of its own, and internal storage's is 0. The message carries the picked PickerFolder, and the screen resolves its label the way breadcrumbs do - so copying into the root reads 'Copied to Internal storage', which is the case a plain path.name would have got wrong.

Four tests: the message names the destination and offers Show; Show opens it; a paste into the folder on screen still names nothing and offers nothing (its destination is the screen); a move to a picked folder offers Undo. All four driven through the view model, and both snackbar variants checked on the phone, including the volume-root one.

detekt's SpreadOperator baseline entries moved with the expression, so the message building is now a small helper with a deliberate suppression and a reason, and the baseline was regenerated: three obsolete entries removed, none added.

CHANGELOG.md

@@ -18,7 +18,8 @@ upload needs a **higher `versionCode`** than every previous upload.
   folder **without leaving the one you are in**. The files stay selected afterwards, so sending the same
   set to a second destination is two taps. A name that already exists there asks exactly what Paste asks,
   naming that folder; progress belongs to the same operation notification, and a move clears the selection
-  because those rows are gone. Underneath it is the paste path with an explicit target: the engine was
+  because those rows are gone. A finished copy answers with **"Copied to *folder*"** and a **Show** button
+  that opens the destination — so the file you just put somewhere is one tap away from being looked at. Underneath it is the paste path with an explicit target: the engine was
   always target-agnostic, so the new part is the picker and the rules around it.
 
 - **Several files can be renamed at once, numbered in a series that carries on.** Selecting more