feat: Discard all, claude-style image pastes, large local drops, per-account / list

- Changes panel: **Discard all** beside Commit discards every non-conflicted
  file in one `discard`, after a dialog naming how many untracked files go.
- Terminal: a `claude` pane gets dropped/pasted images as bare paths (shown as
  `[Image #n]`) and other files as `@` mentions (`claudePastes`); a local
  browser's copied `file://` paths and text-drag file lists paste by path.
- `POST /api/run/drop-file`: a loopback browser outside server mode may drop
  up to 2 GB, streamed to disk; remote stays 20 MB.
- cc-config skills/commands/plugins read the USER scope of the account the
  pane runs as (S3 member home by `cwd`), never another user's or the host's
  for a non-admin without an account; the run form passes its cwd to plugins.

client/src/components/lanes/__tests__/LaneChangesPanel.test.tsx

@@ -770,6 +770,24 @@ describe("LaneChangesPanel", () => {
     });
   });
 
+  it("discards every file at once only after the dialog is confirmed", async () => {
+    const user = userEvent.setup();
+    render(<LaneChangesPanel laneId={7} />);
+    await screen.findByTestId("lane-changes-overview");
+
+    vi.mocked(confirmDialog).mockResolvedValueOnce(false);
+    await user.click(screen.getByTestId("lane-changes-discard-all"));
+    expect(api.lanes.gitAction).not.toHaveBeenCalled();
+
+    await user.click(screen.getByTestId("lane-changes-discard-all"));
+    await waitFor(() =>
+      expect(api.lanes.gitAction).toHaveBeenCalledWith(7, "discard", {
+        paths: ["server/lib/git-ops.js", "notes.txt", "docs/API.md"],
+        confirm: true,
+      })
+    );
+  });
+
   it("right-click on a changed file offers Commit File, a two-click discard, copy path and patch", async () => {
     const user = userEvent.setup();
     render(<LaneChangesPanel laneId={7} />);