feat: edit in the Changes panel, git graph history, plan quota (v2.3.0)

- Changes panel: a working file opens in a CodeMirror editor with its diff
  inline (DiffEditor.tsx, @codemirror/merge, lazy-loaded); Changes folds the
  unchanged lines, Whole file shows them; side by side at 50/50 and full
  width; a Revert per block; original from HEAD or the branch's merge base
  (`mergeBase` on GET /git/changes?range=branch)
- Every diff: green = line added whole, red = removed whole, blue = edited
  in place (--diff-mod)
- History drawn as a commit graph (#58: `parents` on GET /git/log,
  --date-order; lib/commitGraph.ts)
- Per-workspace never-stage list, drawn orange in the Files tree (--kept);
  closed Terminal rows past three deleted
- Status bar plan quota for Claude (per account) and Codex
  (GET /api/pricing/quota, server/lib/quota.js); compact hover panel that
  stays open, Refresh button with a spinner
- Settings → Appearance holds language, theme and pet; Ctrl+Shift+C copies;
  compact sidebar navigation and short session times

server/lib/dashboard-runs.js

@@ -263,12 +263,28 @@ const abandonStmt = db.prepare(`
   WHERE id = ? AND status IN ('running', 'spawning')
 `);
 
+/** Closed Terminal tabs kept per lane — what the sidebar lists
+ *  (`CLOSED_TERMINALS` in WorkspaceSessionList.tsx). */
+const CLOSED_SHELLS_KEPT = 3;
+// A shell has no session, so its row is only that list's entry: one the list
+// cannot show is dropped, or removing the shown ones uncovers older ones.
+const pruneShellsStmt = db.prepare(`
+  DELETE FROM dashboard_runs WHERE id IN (
+    SELECT id FROM (
+      SELECT id, ROW_NUMBER() OVER (PARTITION BY lane_id ORDER BY started_at DESC) AS n
+      FROM dashboard_runs
+      WHERE tool = 'shell' AND status NOT IN ('running', 'spawning')
+    ) WHERE n > ${CLOSED_SHELLS_KEPT}
+  )
+`);
+
 /**
  * Flags `abandoned` every row still marked running/spawning whose pane is
  * gone — the pane's process quit (Ctrl+C, `exit`), or the machine rebooted.
  * A pane is a tmux session, which outlives a server restart, so liveness is
  * asked of `isAlive(id)` (tmux), never assumed from the restart. Run at boot
- * and on the server's run-heal beat.
+ * and on the server's run-heal beat, which also drops the closed Terminal
+ * tabs past the newest {@link CLOSED_SHELLS_KEPT} of each lane.
  *
  * Returns the number of rows updated.
  */
@@ -278,6 +294,7 @@ function reconcileOrphans(isAlive = () => false) {
     for (const { id } of runningStmt.all()) {
       if (!isAlive(id)) changes += abandonStmt.run(id).changes;
     }
+    pruneShellsStmt.run();
     return changes;
   } catch {
     return 0;