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.

docs/CODE_MAP.md

@@ -2,7 +2,7 @@
 
 Generated from the source by `tools/make-code-map.py` - do not edit by hand. Regenerate it after a change (`python3 tools/make-code-map.py`); `--check` exits non-zero when this file is stale.
 
-79 source files, 13393 lines - 35 test files, 404 tests. The behaviour index at the end lists every test name, and in this project a test name is a sentence about what the app does, so it doubles as the specification.
+79 source files, 13481 lines - 35 test files, 409 tests. The behaviour index at the end lists every test name, and in this project a test name is a sentence about what the app does, so it doubles as the specification.
 
 Start at `AGENTS.md`. What is done, and why: `docs/ROADMAP.md` and `CHANGELOG.md`. What was verified by hand rather than by a test: `docs/EDGE_CASE_TESTING.md`.
 
@@ -100,10 +100,10 @@ The browser screen: view model, state, list and grid, dialogs, selection bar
 | `BrowserDetailPane.kt` | 131 | The second pane of the wide layout: what is inside the folder the user picked, or a preview and the details of the file they picked. DetailPane(), FolderPreview(), ImagePreview() | - |
 | `BrowserDialogs.kt` | 385 | The Copy to… / Move to… picker. TransferToDialog(), titleFor(), hereFor(), BatchRenameDialog(), PREVIEW_NAMES, batchRenameNote(), NameDialog(), ConfirmDialog(), ConflictDialog() | `BrowserDialogsTest` (5) |
 | `BrowserRoots.kt` | 270 | A row on the root screen: a volume, with its free space when the platform reports it. RootRow(), itemCountLabel(), EmptyState(), LibrarySectionHeader(), BookmarkSectionHeader(), SectionHeader(), BookmarkRow(), LibraryRow(), Breadcrumbs() | `BrowserRootsTest` (4) |
-| `BrowserScreen.kt` | 603 | BrowserScreen() | - |
+| `BrowserScreen.kt` | 622 | The text of a snackbar message. BrowserScreen(), messageText() | - |
 | `BrowserTopBar.kt` | 238 | The browser's app bar: title, up, the favourite star, and the search / sort / overflow actions. BrowserTopBar(), SEARCH_FIELD_WIDTH | `BrowserTopBarTest` (4) |
-| `BrowserUiState.kt` | 348 | One immutable description of everything the browser shows. ViewMode, SearchScope, Clipboard, PickerFolder, TransferPicker, UiMessage, ConflictPrompt, RootItem, Bookmark, DetailFocus, Undo, UndoMove, Overlay, BrowserUiState | - |
-| `BrowserViewModel.kt` | 2392 | Drives the browser screen. BrowserViewModel, ArchivePreview | `BrowserViewModelTest` (97) |
+| `BrowserUiState.kt` | 379 | One immutable description of everything the browser shows. ViewMode, SearchScope, Clipboard, PickerFolder, TransferPicker, MessageAction, UiMessage, ConflictPrompt, RootItem, Bookmark, DetailFocus, Undo, UndoMove, Overlay, BrowserUiState | - |
+| `BrowserViewModel.kt` | 2430 | Drives the browser screen. BrowserViewModel, ArchivePreview | `BrowserViewModelTest` (102) |
 | `DetailsSheet.kt` | 109 | Name, location, size, type and modified date for one entry. DetailsSheet(), DetailLines(), DetailLine() | - |
 | `EntryIntents.kt` | 58 | Wraps an entry's path in a content:// URI another app may read. contentUriFor(), viewIntent(), shareIntent() | - |
 | `IncomingBar.kt` | 60 | The bar shown while another app is waiting on this one. IncomingBar() | - |
@@ -581,7 +581,7 @@ Every test name in the suite, by file: the fastest way to see whether something
 - a library or the root list has nothing to star
 - the star gives way to the search field
 
-### `ui/browser/BrowserViewModelTest.kt` (97)
+### `ui/browser/BrowserViewModelTest.kt` (102)
 
 - starts on the root list
 - opening a folder lists it with directories first and natural order
@@ -596,6 +596,11 @@ Every test name in the suite, by file: the fastest way to see whether something
 - the picker walks up to the volumes and back down
 - a conflicting destination asks before overwriting, naming that folder
 - cancelling the picker copies nothing
+- a copy says where it went and offers to show it
+- show takes the user to the folder the copy went to
+- a paste into the folder on screen names no destination and offers no action
+- the message's undo action is the undo
+- a move to a chosen folder offers undo rather than show
 - navigating up goes to the parent then to the roots
 - selection survives toggling and clears on navigation
 - a file with no preview of its own is handed to the system