feat(lanes,run,pricing): Changes sidebar editor, staged groups, image drop, auto pricing

- Changes panel at full screen: the whole Files view (finder, expand-all,
  tree) becomes a left sidebar and the Files tab is dropped; a working-copy
  file opens straight into the editor (Save/Cancel live once the text
  differs, Cancel restores it, Whole file toggles back to the diff), and the
  page is height-locked so the editor no longer collapses with no live run.
- Overview splits into Staged Changes / Changes groups in the work range.
- A changed file's whole tree row takes its status tint.
- Drag an image onto the lane terminal: POST /api/run/drop-image saves it
  (png/jpeg/gif/webp, random name, 0600, pruned after a day) and the path
  is pasted into the pane, which is how claude attaches it.
- Claude Opus 5.5 gets its own pricing row (4/20/0.2/5/8, fast 8/40);
  claude-opus-5% had been pricing it as Opus 5.
- server/lib/pricing-sync.js: a model family used in token_usage with no
  row of its own is inserted from LiteLLM's public price list, never
  updated; off with AGENTHUB_PRICING_SYNC=0. repo-links allows exactly
  that one third-party GitHub raw URL.

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

@@ -112,6 +112,9 @@
   "changes.size.full": "Full screen",
   "changes.stageAll": "Stage all ({{count}})",
   "changes.unstageAll": "Unstage all ({{count}})",
+  "changes.dropEdits": "Discard your unsaved edits to this file?",
+  "changes.stagedGroup": "Staged Changes",
+  "changes.unstagedGroup": "Changes",
   "changes.stage": "Stage this file",
   "changes.title": "Changes",
   "changes.truncated": "Some changes were left out to keep this panel responsive.",

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

@@ -164,5 +164,11 @@
     "input": "Input",
     "label": "Context",
     "output": "Output"
+  },
+  "drop": {
+    "hint": "Drop image to attach",
+    "uploading": "Uploading image…",
+    "failed": "Could not attach the image",
+    "imagesOnly": "Only images can be dropped here"
   }
 }

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

@@ -112,6 +112,9 @@
   "changes.size.full": "Toàn màn hình",
   "changes.stageAll": "Stage tất cả ({{count}})",
   "changes.unstageAll": "Bỏ stage tất cả ({{count}})",
+  "changes.dropEdits": "Bỏ các chỉnh sửa chưa lưu của file này?",
+  "changes.stagedGroup": "Đã stage",
+  "changes.unstagedGroup": "Thay đổi",
   "changes.stage": "Đưa file này vào index",
   "changes.title": "Thay đổi",
   "changes.truncated": "Một phần thay đổi đã bị lược bớt để bảng này còn mượt.",

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

@@ -163,5 +163,11 @@
     "input": "Input",
     "label": "Context",
     "output": "Output"
+  },
+  "drop": {
+    "hint": "Thả ảnh để đính kèm",
+    "uploading": "Đang tải ảnh lên…",
+    "failed": "Không đính kèm được ảnh",
+    "imagesOnly": "Chỉ thả được ảnh vào đây"
   }
 }