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/LaneChangesPanel.tsx

@@ -1422,6 +1422,27 @@ export function LaneChangesPanel({
     }
   };
 
+  // Discard all: every non-conflicted file in one `discard`, asked once in a
+  // dialog that names how many untracked files it will delete.
+  const discardAll = async () => {
+    const rows = files.filter((f) => !f.conflicted);
+    if (!rows.length) return;
+    const ok = await confirmDialog({
+      title: t("changes.discardAllTitle"),
+      message: t("changes.discardAllConfirm", {
+        count: rows.length,
+        untracked: rows.filter((f) => f.untracked).length,
+      }),
+      confirmLabel: t("changes.discardAll"),
+    });
+    if (ok)
+      await act(
+        "discard",
+        rows.map((f) => f.path),
+        true
+      );
+  };
+
   // resolve / merge-commit / merge-abort: same shape as `act`, other body.
   const mergeAct = async (
     action: "resolve" | "merge-commit" | "merge-abort",
@@ -2756,6 +2777,17 @@ export function LaneChangesPanel({
                     >
                       {t(amend ? "changes.amendAndPush" : "changes.commitAndPush")}
                     </button>
+                    <button
+                      type="button"
+                      data-testid="lane-changes-discard-all"
+                      disabled={busy}
+                      onClick={() => void discardAll()}
+                      title={t("changes.discardAllTitle")}
+                      className="shrink-0 flex items-center gap-1 rounded border border-border-light px-1.5 py-0.5 text-[11px] text-status-danger hover:bg-status-danger/10 disabled:cursor-not-allowed disabled:opacity-40"
+                    >
+                      <Trash2 className="h-3 w-3" aria-hidden />
+                      {t("changes.discardAll")}
+                    </button>
                   </div>
                 </div>
               )}