♻️ refactor(client): 浏览器半拆成 src 模块，client.js 改由构建产出

src/client/platform.js

@@ -0,0 +1,105 @@
+/**
+ * Every browser and platform fact this plugin reads, in one seam.
+ *
+ * Nothing here owns state or decides anything: the window's visibility, the
+ * notification permission, the notification icon, and the one platform hint the
+ * settings copy uses. Each read is contained, because a page a plugin does not
+ * control may hide any of them — and because a contained read is what lets the
+ * delivery path keep going when the answer is unreadable.
+ *
+ * @module @dsh-plugin/session-notify/client/platform
+ */
+
+/**
+ * The window's Notification constructor, or undefined when this environment has
+ * none (a plain Node test, or a browser without the API).
+ * @returns the constructor, or undefined.
+ */
+export function notificationApi() {
+  const Ctor = globalThis.Notification
+  return typeof Ctor === 'function' ? Ctor : undefined
+}
+
+/** Permission lookup that never throws in a browser without the API. */
+export function notificationPermission() {
+  const Ctor = notificationApi()
+  if (Ctor === undefined) return 'unsupported'
+  const permission = Ctor.permission
+  if (permission === 'granted' || permission === 'denied' || permission === 'default') return permission
+  return 'default'
+}
+
+/**
+ * Whether the Harness window is somewhere the user cannot see the app.
+ *
+ * Two independent browser facts are consulted, and ANY of them counts as "not
+ * in the foreground": the page's visibility and the document's focus. They are
+ * read at delivery time rather than remembered from an event, because a missed
+ * blur in the desktop shell made this plugin believe the window was in front
+ * and swallow the alert.
+ * @returns whether the alert must go to the system notification channel.
+ */
+export function windowIsAway() {
+  try {
+    if (document.visibilityState === 'hidden') return true
+  } catch {
+    /* an unreadable visibility state leaves the focus fact */
+  }
+  try {
+    if (typeof document.hasFocus === 'function') return !document.hasFocus()
+  } catch {
+    /* an unreadable focus state leaves the default below */
+  }
+  return false
+}
+
+/** Read the window's live focus state rather than a cached value. */
+export function currentFocus() {
+  return !windowIsAway()
+}
+
+/** Focus the window without letting a refusal stop the navigation. */
+export function focusWindow() {
+  try {
+    globalThis.focus?.()
+  } catch {
+    /* focus is best effort on every platform */
+  }
+}
+
+/**
+ * The system-notification icon, built once when this bundle materializes: this
+ * deployment's own static URL when the page serves this package's assets, else
+ * the SVG inline. Icons are cosmetic on every platform, so each step is
+ * contained — and materialization happens on first import, not when the bundle
+ * script runs, so a page that never activates the plugin never gets here.
+ * @type {string | undefined} an icon URL, or undefined when neither form works.
+ */
+export const systemIcon = (() => {
+  try {
+    const url = new URL('./icon.svg', document.baseURI).href
+    if (url !== '') return url
+  } catch {
+    /* fall through to the inline form */
+  }
+  try {
+    const svg = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16"><path d="M8 2.35C5.7 2.35 3.83 4.22 3.83 6.52V9.02L3.06 11.1C2.99 11.29 3.13 11.48 3.33 11.48H12.67C12.87 11.48 13.01 11.29 12.94 11.1L12.17 9.02V6.52C12.17 4.22 10.3 2.35 8 2.35Z" fill="none" stroke="%23247bbf" stroke-width="1.2"/><path d="M6.3 12.75C6.52 13.66 7.2 14.28 8 14.28C8.8 14.28 9.48 13.66 9.7 12.75" fill="none" stroke="%23247bbf" stroke-width="1.2" stroke-linecap="round"/></svg>'
+    return `data:image/svg+xml,${svg}`
+  } catch {
+    return undefined
+  }
+})()
+
+/** One best-effort platform hint, used for settings help text only. */
+export function platformKey() {
+  try {
+    const agent = navigator.userAgentData
+    const platform = String((agent?.platform ?? navigator.platform) || navigator.userAgent || '')
+    if (/win/i.test(platform)) return 'win'
+    if (/mac|iphone|ipad/i.test(platform)) return 'mac'
+    if (/linux|x11/i.test(platform)) return 'linux'
+  } catch {
+    /* an unreadable navigator keeps the neutral hint */
+  }
+  return 'plain'
+}