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/i18n/locales/en/lanes.json

@@ -531,6 +531,9 @@
   "changes.unversionedGroup": "Unversioned Files",
   "changes.commitTicked": "Commit ({{count}})",
   "changes.commitAndPush": "Commit and Push",
+  "changes.discardAll": "Discard all",
+  "changes.discardAllTitle": "Discard all changes?",
+  "changes.discardAllConfirm": "Every change in {{count}} file(s) goes back to the last commit, and {{untracked}} new file(s) git does not track yet are deleted. This cannot be undone.",
   "changes.amendAndPush": "Amend and Push",
   "changes.pushFailed": "Committed, but the push failed: {{error}}",
   "changes.tickFile": "Include {{path}} in the commit",

client/src/i18n/locales/vi/lanes.json

@@ -531,6 +531,9 @@
   "changes.unversionedGroup": "File chưa theo dõi",
   "changes.commitTicked": "Commit ({{count}})",
   "changes.commitAndPush": "Commit và Push",
+  "changes.discardAll": "Bỏ tất cả",
+  "changes.discardAllTitle": "Bỏ tất cả thay đổi?",
+  "changes.discardAllConfirm": "Mọi thay đổi trong {{count}} file sẽ trở về commit cuối, và {{untracked}} file mới chưa được git theo dõi sẽ bị xoá. Không thể hoàn tác.",
   "changes.amendAndPush": "Amend và Push",
   "changes.pushFailed": "Đã commit, nhưng push thất bại: {{error}}",
   "changes.tickFile": "Đưa {{path}} vào commit",