fix(admin): address Copilot review findings

- Reflect built-in defaults for boolean settings (ALLOW_PRIVATE_URLS
  defaults on) and allow clearing a saved boolean back to default,
  so the SSRF toggle matches actual runtime behavior.
- Harden JSON loading: filter settings values to strings only, and
  schema-validate stored ADMIN_PROVIDERS entries, dropping malformed
  ones instead of letting them reach runtime code.
- Set beforeunload returnValue so the unsaved-changes prompt shows in
  all browsers; reject non-finite numbers in settings validation.
- Fix README/CN/JA docs that claimed the panel auto-generates
  AI_MODELS_CONFIG (providers are merged at read time, not written).
- Add unit tests for corrupted-file value filtering and provider
  schema validation.

tests/unit/admin-providers.test.ts

@@ -3,8 +3,10 @@ import os from "os"
 import path from "path"
 import { afterEach, beforeEach, describe, expect, it } from "vitest"
 import {
+    ADMIN_PROVIDERS_KEY,
     adminProvidersToConfig,
     deriveEnvUpdates,
+    loadAdminProviders,
     mergeSecrets,
     type StoredAdminProvider,
     validateAdminProviders,
@@ -328,3 +330,38 @@ describe("validateAdminProviders", () => {
         expect(validateAdminProviders(list)).toBeNull()
     })
 })
+
+describe("loadAdminProviders", () => {
+    it("returns [] when nothing is stored", () => {
+        expect(loadAdminProviders()).toEqual([])
+    })
+
+    it("loads valid stored providers", () => {
+        saveSettings({ [ADMIN_PROVIDERS_KEY]: JSON.stringify([provider()]) })
+        expect(loadAdminProviders()).toHaveLength(1)
+    })
+
+    it("drops malformed entries and keeps valid ones", () => {
+        saveSettings({
+            [ADMIN_PROVIDERS_KEY]: JSON.stringify([
+                provider({ id: "good" }),
+                { id: "missing-fields" }, // no provider/models
+                { provider: "openai", models: ["x"] }, // no id
+                "not-an-object",
+            ]),
+        })
+        const loaded = loadAdminProviders()
+        expect(loaded).toHaveLength(1)
+        expect(loaded[0].id).toBe("good")
+    })
+
+    it("returns [] when the stored value is not an array", () => {
+        saveSettings({ [ADMIN_PROVIDERS_KEY]: JSON.stringify({ nope: true }) })
+        expect(loadAdminProviders()).toEqual([])
+    })
+
+    it("returns [] on invalid JSON", () => {
+        saveSettings({ [ADMIN_PROVIDERS_KEY]: "{ broken" })
+        expect(loadAdminProviders()).toEqual([])
+    })
+})

tests/unit/admin-settings.test.ts

@@ -39,6 +39,31 @@ describe("loadSettings", () => {
         )
         expect(loadSettings()).toEqual({ TEST_ADMIN_VAR: "abc" })
     })
+
+    it("drops non-string values from a corrupted file", () => {
+        fs.writeFileSync(
+            process.env.SETTINGS_FILE!,
+            JSON.stringify({
+                version: 1,
+                values: {
+                    GOOD: "ok",
+                    NUM: 5,
+                    OBJ: { nested: true },
+                    ARR: [1, 2],
+                    NULL: null,
+                },
+            }),
+        )
+        expect(loadSettings()).toEqual({ GOOD: "ok" })
+    })
+
+    it("returns empty object when values is null or an array", () => {
+        fs.writeFileSync(
+            process.env.SETTINGS_FILE!,
+            JSON.stringify({ version: 1, values: null }),
+        )
+        expect(loadSettings()).toEqual({})
+    })
 })
 
 describe("applyToEnv / saveSettings", () => {