feat(terminal): a text drag (a Files/Changes row, a skill) is pasted into the pane

xterm.js has no drop handling of its own, so dropped text was lost; the pane
now pastes it as a local terminal does, with a "Drop to paste" hint.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/i18n/locales/en/run.json

@@ -65,6 +65,7 @@
   },
   "drop": {
     "hint": "Drop files or images to attach",
+    "paste": "Drop to paste into the terminal",
     "uploading": "Uploading…",
     "failed": "Could not attach the file",
     "remove": "Remove attachment",

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

@@ -65,6 +65,7 @@
   },
   "drop": {
     "hint": "Thả file hoặc ảnh để đính kèm",
+    "paste": "Thả để dán vào terminal",
     "uploading": "Đang tải lên…",
     "failed": "Không đính kèm được file",
     "remove": "Bỏ đính kèm",