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>

tools/fetch-icons.ts

@@ -0,0 +1,80 @@
+/**
+ * Downloads character and Arc artwork once, at build time.
+ *
+ * everness is never hotlinked at runtime: the app would break the moment their
+ * paths changed or their CORS policy tightened, and it would be rude besides.
+ * Files land in `public/img/` named by a content hash, so they can be served
+ * `immutable` and a changed icon gets a new name for free.
+ *
+ * The single-file `file://` build does not carry these - inlining 72 images
+ * would multiply its size for decoration. Cards fall back to the character's
+ * name there, which is the information that actually matters.
+ *
+ *   node --experimental-strip-types tools/fetch-icons.ts
+ */
+import { createHash } from "node:crypto";
+import { mkdirSync, readFileSync, writeFileSync, readdirSync, rmSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const root = join(dirname(fileURLToPath(import.meta.url)), "..");
+const outDir = join(root, "public", "img");
+const BASE = "https://everness.info/images";
+
+interface Entry {
+  key: string;
+  path: string;
+}
+
+const gamedata = JSON.parse(readFileSync(join(root, "src/generated/gamedata.json"), "utf8"));
+
+const entries: Entry[] = [
+  ...gamedata.espers.map((esper: { abilityKey: string; icon: string }) => ({
+    key: `esper:${esper.abilityKey}`,
+    path: esper.icon,
+  })),
+  ...gamedata.arcs.map((arc: { id: string; icon: string }) => ({
+    key: `arc:${arc.id}`,
+    path: arc.icon,
+  })),
+].filter((entry) => typeof entry.path === "string" && entry.path.length > 0);
+
+mkdirSync(outDir, { recursive: true });
+// Rebuilt wholesale, so a renamed icon cannot leave an orphan behind.
+for (const name of readdirSync(outDir)) rmSync(join(outDir, name));
+
+const manifest: Record<string, string> = {};
+let bytes = 0;
+let failed = 0;
+
+for (const entry of entries) {
+  const url = `${BASE}${entry.path}.webp`;
+  try {
+    const response = await fetch(url, { headers: { "user-agent": "nte-optimizer build" } });
+    if (!response.ok) {
+      failed += 1;
+      console.warn(`  ${response.status} ${url}`);
+      continue;
+    }
+    const buffer = Buffer.from(await response.arrayBuffer());
+    const hash = createHash("sha256").update(buffer).digest("hex").slice(0, 8);
+    const slug = entry.path.split("/").pop() ?? "icon";
+    const name = `${slug}-${hash}.webp`;
+    writeFileSync(join(outDir, name), buffer);
+    manifest[entry.key] = name;
+    bytes += buffer.byteLength;
+  } catch (error) {
+    failed += 1;
+    console.warn(`  failed ${url}: ${error instanceof Error ? error.message : error}`);
+  }
+}
+
+writeFileSync(
+  join(root, "src", "generated", "icons.json"),
+  `${JSON.stringify({ format: "nte-icons", format_version: 1, files: manifest }, null, 1)}\n`,
+);
+
+console.log(
+  `icons  ${Object.keys(manifest).length} of ${entries.length} fetched` +
+    `${failed > 0 ? `, ${failed} failed` : ""}  ${(bytes / 1024).toFixed(0)} KB`,
+);