feedback6: version 0.2.1 — package.json / package-lock.json / APP_VERSION (DEV_BUILD turns false: the title-screen dev tag, the boot warning and the package guard go)

- CHANGELOG 0.2.1 (2026-10-07): the streams' lines collected (新功能: the update package and MANIFEST.json; 规则（按官方）:
  联防 on the round's battlefield, 突袭 onto a teammate's half, full potential, the replace dialog for consumables,
  the 外勤医疗 Touch, 凋亡, 贾维's 拉普兰德, the 频次 器物 / leader summons; 界面: the collapse arrow, 自选 picks in the bond
  lists, flyers, enemy animations, the Touch card, Esc in the 自选 picker; 联机与大厅: battle messages while a battle
  loads; 工具与开发: the update build, .gitignore), one intro paragraph.
- README: the dev warning under the title removed, the release badge, 「当前版本 0.2.1」; DESIGN's version line names
  0.2.1 (§26) as the state described; §26's intro says when the dev line shipped.
- Tests: version, docs-consistency, docs-paths, package, i18n-packs, update-package, update-boot 80 / 80.

shared/constants.js

@@ -5,7 +5,7 @@ import { N_ } from './i18n.js';
 export const PROTOCOL_VERSION = 1;
 /** Release version shown to players (title screen, server banner, /healthz). Kept equal to package.json "version"
  * (test/version.test.js); PROTOCOL_VERSION above is the separate wire-format number. */
-export const APP_VERSION = '0.2.1-dev';
+export const APP_VERSION = '0.2.1';
 /** A development build (the public `dev` branch): the title screen, the boot banner and the README say so, and
  * tools/package.mjs refuses to build a release zip from it without --allow-dev. */
 export const DEV_BUILD = /-dev$/.test(APP_VERSION);