feat(keys): harness snippets for every OS + install command when missing

The harness auto-setup scripts were bash-only (heredocs, mkdir -p) — useless
on Windows. Every scripty snippet now exists in two flavors behind a
🐧🍎/🪟 switch (auto-detected from the browser): bash heredocs for
Linux/macOS and PowerShell here-strings ($env:, New-Item, @'..'@,
curl.exe with backtick continuations) for Windows. SDK snippets and GUI
instructions stay OS-independent.

And when detection says a harness is NOT installed on the gateway machine,
the status line now offers its one-line install command for the selected OS
(claude.ai install.sh / install.ps1, npm -g for Codex and OpenCode-on-
Windows, code --install-extension for Continue/Cline) with a copy button.
1 string ×7 languages.

web/js/i18n/de.js

@@ -643,4 +643,5 @@ export default {
   "keys.form.budgetHint": "Überschreiten die Monatsausgaben des Kontos die Grenze, werden Anfragen mit 429 insufficient_quota abgelehnt.",
   "keys.budgetOf": "Budget {b}/Mon.",
   "dash.kpi.orBalance": "OpenRouter-Guthaben",
+  "keys.h.install": "Installieren:",
 };

web/js/i18n/en.js

@@ -636,4 +636,5 @@ export default {
   "keys.form.budgetHint": "Requests are rejected with 429 insufficient_quota once the account's month-to-date spend crosses this.",
   "keys.budgetOf": "budget {b}/mo",
   "dash.kpi.orBalance": "OpenRouter balance",
+  "keys.h.install": "Install:",
 };

web/js/i18n/es.js

@@ -643,4 +643,5 @@ export default {
   "keys.form.budgetHint": "Cuando el gasto del mes supera el techo, las peticiones se rechazan con 429 insufficient_quota.",
   "keys.budgetOf": "presupuesto {b}/mes",
   "dash.kpi.orBalance": "Saldo OpenRouter",
+  "keys.h.install": "Instalar:",
 };

web/js/i18n/fr.js

@@ -643,4 +643,5 @@ export default {
   "keys.form.budgetHint": "Quand les dépenses du mois dépassent le plafond, les requêtes sont rejetées avec 429 insufficient_quota.",
   "keys.budgetOf": "budget {b}/mois",
   "dash.kpi.orBalance": "Solde OpenRouter",
+  "keys.h.install": "Installer :",
 };

web/js/i18n/ru.js

@@ -635,4 +635,5 @@ export default {
   "keys.form.budgetHint": "Когда траты аккаунта за месяц превысят потолок, запросы отклоняются с 429 insufficient_quota.",
   "keys.budgetOf": "бюджет {b}/мес",
   "dash.kpi.orBalance": "Баланс OpenRouter",
+  "keys.h.install": "Установить:",
 };

web/js/i18n/tr.js

@@ -643,4 +643,5 @@ export default {
   "keys.form.budgetHint": "Hesabın aylık harcaması tavanı aşınca istekler 429 insufficient_quota ile reddedilir.",
   "keys.budgetOf": "bütçe {b}/ay",
   "dash.kpi.orBalance": "OpenRouter bakiyesi",
+  "keys.h.install": "Kurulum:",
 };

web/js/i18n/zh.js

@@ -643,4 +643,5 @@ export default {
   "keys.form.budgetHint": "当账户当月支出超过上限时，请求将被拒绝并返回 429 insufficient_quota。",
   "keys.budgetOf": "预算 {b}/月",
   "dash.kpi.orBalance": "OpenRouter 余额",
+  "keys.h.install": "安装：",
 };