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/lib/__tests__/promptAttach.test.ts

@@ -0,0 +1,20 @@
+/**
+ * @file promptAttach.test.ts — `claudePastes`: how files reach a `claude` pane.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+import { describe, expect, it } from "vitest";
+import { claudePastes } from "../promptAttach";
+
+describe("claudePastes", () => {
+  it("pastes each image as its bare path and the other files as one @ mention paste", () => {
+    expect(
+      claudePastes(["/d/drops/a.png", "/d/drops/b-report.pdf", "/d/x.JPG", "/d/c.log"])
+    ).toEqual(["/d/drops/a.png", "/d/x.JPG", "@/d/drops/b-report.pdf @/d/c.log"]);
+  });
+
+  it("keeps a Windows or spaced image path a mention", () => {
+    expect(claudePastes(["C:\\u\\drops\\a.png", "/home/u/my shot.png"])).toEqual([
+      '@C:/u/drops/a.png @"/home/u/my shot.png"',
+    ]);
+  });
+});