Turn the Files tab into a real file manager

Rename, an in-app viewer for text and images, host-to-container drag and
drop, New folder, keyboard operation — plus the pre-existing bugs the new
surface would otherwise have been built on top of.

New Tauri commands (file_commands.rs, registered in lib.rs):

* rename_container_path — `mv -n -- <from> <parent>/<name>` through
  exec_oneshot_as, so the *exit code* is checked. exec_oneshot discards the
  status and interleaves stderr into stdout, which would have made a
  permission failure look like a success. `mv -n` on its own is not enough
  either: GNU coreutils makes its refusal to clobber silent and exits 0, so
  an explicit `test -e` on the destination is what turns a name clash into
  an error the user sees. `mv`'s own words are surfaced, since renames
  outside /workspace legitimately fail on permissions. The new name is
  validated in Rust (no `/`, no NUL, not "." / ".." / empty, ≤255 bytes) —
  it is user text going into argv, and a name with a separator would be a
  move rather than a rename.
* read_container_file — exact bytes via Docker's archive endpoint, returned
  as base64. Deliberately not exec_oneshot, which runs every chunk through
  String::from_utf8_lossy and merges stderr, so it would corrupt any
  non-UTF-8 file and could splice diagnostics into content. Base64 rather
  than Vec<u8> because Tauri serialises a byte vec as a JSON number array.
  Capped and truncation-reporting; the caller picks the cap (images get 5
  MiB against text's 1 MiB, being the kind that blows a text-sized budget)
  and Rust clamps it to 8 MiB regardless.
* create_container_directory — `mkdir` without -p, so a clash is an error
  rather than a silent success. Named for its siblings rather than the bare
  `create_directory` in the brief.

The tar-extraction half of download_container_file is now the shared
fetch_container_file() both commands use, and it abandons the transfer once
a capped read has what it needs.

Frontend:

* Single click selects, double click opens. Directory navigation moved onto
  double click too — a single click used to navigate, which made it
  impossible to select a directory in order to rename it. Rows are now
  focusable and the table is a real `grid`: Enter opens, F2 renames, arrows
  walk the rows. No outline suppression; the global :focus-visible ring is
  what shows focus.
* FileViewerModal (built on ui/Modal, the only correct dialog) renders text
  in a <pre> and images from a revocable blob: URL. tauri.conf.json's
  img-src had neither `data:` nor `blob:`, so an in-app image was blocked by
  CSP; `blob:` is added — revocable, and no megabytes of base64 in the DOM.
  The asset protocol stays disabled. Anything else gets a "Save to host"
  state instead of a broken preview, decided by extension and then by
  sniffing the bytes for NUL.
* Host drag-and-drop uses Tauri's native onDragDropEvent, mirroring
  TerminalView: HTML5 ondrop carries no paths and is blocked in the webview
  on Windows by dragDropEnabled, which the terminal needs. The listener is
  window-wide, so it routes by hit-testing the payload position (physical
  pixels, hence the devicePixelRatio divide) against the pane's rect — a
  hidden pane has a zero-size rect and never matches, which is what keeps
  this and the terminal's listener apart. enter/over/leave drive a drop
  highlight.
* Per-row Download is now "Save to host…"; directories no longer offer it.

Pre-existing bugs fixed:

* Uploaded files landed root:root with a 1970 mtime. tar::Header::new_gnu()
  zeroes uid/gid/mtime and Docker honours the header verbatim, so uploads
  were not writable by `claude`. All four single-file tar builds now go
  through build_single_file_tar() with the container user's ids, read from
  the container because entrypoint.sh remaps them to the host user on Unix
  and deliberately does not on Windows.
* Symlinked directories could not be opened: `find -printf '%y'` reports `l`.
  The listing now prints `%Y` as well, so is_directory dereferences and a
  new is_symlink carries what `%y` used to say. The row labels the link.
* upload_file_to_container had no size cap and did a synchronous fs::read on
  an async worker. Now 256 MiB (matching the terminal drop path) with the
  read and tar build in spawn_blocking, and the host mtime preserved.
* A directory passed to upload reached fs::read and produced an opaque "Is a
  directory". Rejected with an explanation instead — recursive upload is a
  larger feature than this panel needs.
* download_container_file wrote the *first tar entry*, so downloading a
  directory silently produced a garbage file. Non-regular entries are now an
  explicit error.

Tests: 46 new (33 frontend across FilesTab, useFileManager and filePreview;
12 Rust covering the find-output parser and the rename validator, neither of
which had any). 405 frontend / 297 Rust, both green.

No drag-out dependency was added — tauri-plugin-drag is not introduced and
OS drag-out is not attempted; that stays deferred, with "Save to host…" as
the way files leave the container.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBq2rGum6GX7xXgsas1fDc

app/src/hooks/useFileManager.ts

@@ -8,6 +8,8 @@ export function useFileManager(projectId: string) {
   const [entries, setEntries] = useState<FileEntry[]>([]);
   const [loading, setLoading] = useState(false);
   const [error, setError] = useState<string | null>(null);
+  /** Transient "uploading 3 files…" style note, shown beside the breadcrumb. */
+  const [busy, setBusy] = useState<string | null>(null);
 
   const navigate = useCallback(
     async (path: string) => {
@@ -36,11 +38,13 @@ export function useFileManager(projectId: string) {
     navigate(currentPath);
   }, [currentPath, navigate]);
 
+  /** Copy an entry out to a host path the user picks. */
   const downloadFile = useCallback(
     async (entry: FileEntry) => {
       try {
         const hostPath = await save({ defaultPath: entry.name });
         if (!hostPath) return;
+        setError(null);
         await commands.downloadContainerFile(projectId, entry.path, hostPath);
       } catch (e) {
         setError(String(e));
@@ -49,26 +53,99 @@ export function useFileManager(projectId: string) {
     [projectId],
   );
 
+  /**
+   * Copy host files into the current directory. Shared by the Upload button and
+   * the native drag-drop listener, so a dropped file and a picked one take the
+   * same path — including the one refresh at the end rather than one per file.
+   */
+  const uploadPaths = useCallback(
+    async (hostPaths: string[]) => {
+      if (hostPaths.length === 0) return;
+      setError(null);
+      setBusy(`Uploading ${hostPaths.length} item${hostPaths.length > 1 ? "s" : ""}…`);
+      const failures: string[] = [];
+      try {
+        for (const hostPath of hostPaths) {
+          try {
+            await commands.uploadFileToContainer(projectId, hostPath, currentPath);
+          } catch (e) {
+            failures.push(String(e));
+          }
+        }
+      } finally {
+        setBusy(null);
+      }
+      // Re-list first: `navigate` clears the error, so reporting before it
+      // would wipe the very message the user needs.
+      await navigate(currentPath);
+      if (failures.length > 0) setError(failures.join(" · "));
+    },
+    [projectId, currentPath, navigate],
+  );
+
   const uploadFile = useCallback(async () => {
     try {
-      const selected = await openDialog({ multiple: false, directory: false });
+      const selected = await openDialog({ multiple: true, directory: false });
       if (!selected) return;
-      await commands.uploadFileToContainer(projectId, selected as string, currentPath);
-      await navigate(currentPath);
+      await uploadPaths(Array.isArray(selected) ? selected : [selected as string]);
     } catch (e) {
       setError(String(e));
     }
-  }, [projectId, currentPath, navigate]);
+  }, [uploadPaths]);
+
+  /**
+   * Rename in place. `newName` is a bare name — Rust rejects anything with a
+   * `/` in it, so this can never turn into a move. Resolves true on success so
+   * the caller knows whether to leave edit mode.
+   */
+  const renameEntry = useCallback(
+    async (entry: FileEntry, newName: string) => {
+      const trimmed = newName.trim();
+      if (!trimmed || trimmed === entry.name) return true;
+      try {
+        setError(null);
+        await commands.renameContainerPath(projectId, entry.path, trimmed);
+        await navigate(currentPath);
+        return true;
+      } catch (e) {
+        setError(String(e));
+        return false;
+      }
+    },
+    [projectId, currentPath, navigate],
+  );
+
+  const createFolder = useCallback(
+    async (name: string) => {
+      const trimmed = name.trim();
+      if (!trimmed) return true;
+      try {
+        setError(null);
+        await commands.createContainerDirectory(projectId, currentPath, trimmed);
+        await navigate(currentPath);
+        return true;
+      } catch (e) {
+        setError(String(e));
+        return false;
+      }
+    },
+    [projectId, currentPath, navigate],
+  );
 
   return {
     currentPath,
     entries,
     loading,
     error,
+    busy,
+    setError,
     navigate,
     goUp,
     refresh,
     downloadFile,
     uploadFile,
+    uploadPaths,
+    renameEntry,
+    createFolder,
   };
 }