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/db.js

@@ -834,6 +834,9 @@ const DEFAULT_PRICING = [
   ["claude-fable-5%", "Claude Fable 5", 10, 50, 1, 12.5, 20, 0, 0],
   ["claude-mythos-5%", "Claude Mythos 5", 10, 50, 1, 12.5, 20, 0, 0],
   // Opus family (fast mode available on 5 / 4.6 / 4.7 / 4.8)
+  // 5.5 is cheaper than 5 and "claude-opus-5%" would swallow it — own row
+  // (longest pattern wins in calculateCost).
+  ["claude-opus-5-5%", "Claude Opus 5.5", 4, 20, 0.2, 5, 8, 8, 40],
   ["claude-opus-5%", "Claude Opus 5", 5, 25, 0.5, 6.25, 10, 10, 50],
   ["claude-opus-4-8%", "Claude Opus 4.8", 5, 25, 0.5, 6.25, 10, 10, 50],
   ["claude-opus-4-7%", "Claude Opus 4.7", 5, 25, 0.5, 6.25, 10, 30, 150],