feat: NTE gear optimizer web app

Client-side optimizer for Neverness to Everness console builds. Imports a
gear export from nte-history-exporter, keeps it in IndexedDB, and solves for
the best module placement per character or across a team.

- domain/: pure ports of the Python research scripts (shapes, cartridges,
  board tiling, stats, scoring, set bonuses, Arc effects, sheet prediction).
  No DOM, no storage imports, so they stay worker-safe and Node-testable.
- solver/: single-character solve with branch and bound, plus a three-phase
  team solve (portfolio, leximin, column generation) over disjoint item sets.
  Runs in a Worker when one can be constructed, inline otherwise.
- db/: three storage tiers selected by use rather than feature detection,
  fail-closed import validation, and undo that restores both sides of a steal.
- ui/: React 19 views for items, characters and teams; the board is drawn as
  the deliverable rather than a score.
- Two build targets: a hosted bundle and a single self-contained nte.html
  with no external requests.

Values the model cannot measure are reported as unavailable rather than
guessed: cartridge set bonuses, the level 80 base-stat multiplier, and the
distinction between "optimal for this packing" and globally optimal.

145 tests, tsc clean, both build targets clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/ui/Board.tsx

@@ -0,0 +1,60 @@
+/**
+ * A character's console grid.
+ *
+ * Blocked cells are drawn as holes, free cells as the piece covering them, and
+ * borders only where a piece meets something else - so a build reads as six to
+ * eight objects rather than twenty squares.
+ */
+import { pieceColour, renderBoard } from "../domain/render.ts";
+
+export interface BoardProps {
+  cells: readonly number[];
+  placement: readonly number[];
+  pieces: number;
+  /** Called with the piece index under the pointer, or null. */
+  onHover?: (piece: number | null) => void;
+  labelFor?: (piece: number) => string;
+  size?: number;
+}
+
+export function Board({
+  cells,
+  placement,
+  pieces,
+  onHover,
+  labelFor,
+  size = 34,
+}: BoardProps) {
+  const render = renderBoard(cells, placement);
+  const free = new Set(cells);
+
+  return (
+    <div
+      className="board"
+      style={{ gridTemplateColumns: `repeat(${render.cols}, ${size}px)` }}
+      onPointerLeave={() => onHover?.(null)}
+    >
+      {Array.from({ length: render.rows * render.cols }, (_, index) => {
+        if (!free.has(index)) {
+          return <div key={index} className="board-cell board-cell--blocked" />;
+        }
+        const cell = render.cells.find((entry) => entry.cell === index)!;
+        return (
+          <div
+            key={index}
+            className="board-cell"
+            title={labelFor?.(cell.piece)}
+            onPointerEnter={() => onHover?.(cell.piece)}
+            style={{
+              background: pieceColour(cell.piece, pieces),
+              borderTopWidth: cell.top ? 2 : 0,
+              borderRightWidth: cell.right ? 2 : 0,
+              borderBottomWidth: cell.bottom ? 2 : 0,
+              borderLeftWidth: cell.left ? 2 : 0,
+            }}
+          />
+        );
+      })}
+    </div>
+  );
+}