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.

server/README.md

@@ -703,6 +703,7 @@ HTTP surface for the tmux-backed terminal run: one session per lane, named `agen
 | `GET`    | `/api/run/binary[?tool=]`     | Probe whether the CLI is on `PATH`. `?tool=codex` probes Codex; omitted or `?tool=claude` probes Claude; anything else is `400 EBADTOOL`. Returns `{ found, path }` |
 | `GET`    | `/api/run/tmux`               | `{ available }` — whether the `tmux` binary exists |
 | `GET`    | `/api/run/cwds`               | Suggested cwds (dashboard, home, recent from sessions) |
+| `POST`   | `/api/run/drop-image`          | An image dropped on the Workspace terminal. Raw body, `Content-Type` one of `image/png\|jpeg\|gif\|webp`, ≤20 MB. Saved `0600` under `<tmpdir>/agenthub-drops-<uid>/` with a RANDOM name (nothing from the request names the file); files older than a day are pruned on each write. Answers `{ path }`, which `TerminalView` pastes into the pane — what a local terminal does on a drop, and how `claude` attaches the image. 400 for any other type |
 | `GET`    | `/api/run/files?cwd=…&q=…`    | Fuzzy file search inside `cwd` for the run panel's `@`-file autocomplete. Skips `node_modules`, `.git`, `dist`, `build`, `.next`, `.cache`, `coverage`, `vendor`, etc. Cwd is required and must exist; results are capped and ranked by basename match |
 | `POST`   | `/api/run`                    | Create-or-adopt the lane's tmux session. Body: `{ laneId, cwd, initialPrompt?, model?, permissionMode?, effort?, resumeSessionId? }`. The CLI comes from the lane row, never from the body. An existing session whose pane sits at a shell prompt gets the argv typed into it; a pane already running a program is adopted unchanged |
 | `GET`    | `/api/run/:id`                | One run handle, or 404 once its tmux session is gone |