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/__tests__/pricing-calc.test.js

@@ -324,3 +324,42 @@ describe("calculateCost — date-effective (intro) pricing", () => {
     );
   });
 });
+
+describe("DEFAULT_PRICING — Opus 5.5", () => {
+  it("prices claude-opus-5-5 at its own rates, not Opus 5's", () => {
+    const os = require("os");
+    const path = require("path");
+    process.env.DASHBOARD_DB_PATH = path.join(
+      os.tmpdir(),
+      `pricing-opus55-${Date.now()}-${process.pid}.db`
+    );
+    const { DEFAULT_PRICING } = require("../db");
+    const rules = DEFAULT_PRICING.map(([p, n, i, o, cr, cw, cw1h, fi, fo]) => ({
+      model_pattern: p,
+      display_name: n,
+      input_per_mtok: i,
+      output_per_mtok: o,
+      cache_read_per_mtok: cr,
+      cache_write_per_mtok: cw,
+      cache_write_1h_per_mtok: cw1h,
+      fast_input_per_mtok: fi,
+      fast_output_per_mtok: fo,
+    }));
+    // A real session: Claude Code's /cost reported $2.72 for exactly these
+    // counts (all cache writes at the 1h tier); Opus 5's rates gave $4.86.
+    const r = calculateCost(
+      [
+        bucket({
+          model: "claude-opus-5-5",
+          input_tokens: 102,
+          output_tokens: 25_408,
+          cache_read_tokens: 5_866_977,
+          cache_write_tokens: 129_432,
+          cache_write_1h_tokens: 129_432,
+        }),
+      ],
+      rules
+    );
+    assert.equal(r.total_cost.toFixed(2), "2.72");
+  });
+});