fix(desktop updates): Linux package installs update via their package manager

Reported on CachyOS: "Check for Updates → The update downloaded but
couldn't be installed … Permission denied (os error 13) at path
/usr/bin/tauri_current_app…". The app was installed from the Arch package;
Tauri's Linux updater can only replace an AppImage.

With cinny-desktop's new update_install_kind command:
- pacman / deb installs: the toast says the update is available and opens
  Settings → General → App Updates, which shows the package-manager command
  (`sudo pacman -U …pkg.tar.zst`, or the .deb + `sudo apt install`) with
  Copy command and Download package — no Install & Restart that can't work.
  "Copied" only when the clipboard write actually succeeded.
- other distros: a link to the downloads page.
- Windows, AppImage, and desktop builds without the command: unchanged
  in-app update.
- a native "package-managed" refusal shows the same help.

Tests: unit (kinds, commands, refusal detection); in the real client with a
simulated desktop bridge: pacman → toast + Settings command/buttons,
install never attempted; older desktop → in-app flow as before. Unit 1321,
Playwright 26 passed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/settings/general/General.tsx

@@ -112,7 +112,13 @@ import {
 import { chromeTranslationEngine } from '../../../utils/translation/chromeEngine';
 import { SequenceCardStyle } from '../styles.css';
 import { UpdateProgress, useTauriUpdater } from '../../../hooks/useTauriUpdater';
-import { describeUpdateError, manualDownloadUrl } from '../../../utils/updateErrors';
+import {
+  describeUpdateError,
+  isPackageManagedError,
+  manualDownloadUrl,
+  packageUpdateHelp,
+} from '../../../utils/updateErrors';
+import { copyToClipboard } from '../../../utils/dom';
 import { isTauri as isTauriEnv, invokeTauri, tauriInvoke } from '../../../hooks/useTauri';
 import { useKeychainMirrorStatus } from '../../../state/keychainMirror';
 import { isSafeGlobalToggleKey } from '../../../hooks/useCallHotkeys';
@@ -2794,12 +2800,76 @@ function updateProgressText(progress: UpdateProgress | undefined): string {
   return `Downloading update… ${pct}% (${formatMb(downloaded)} of ${formatMb(total)})${attempt}`;
 }
 
-function AppUpdates() {
-  const { isTauri, status, check, install } = useTauriUpdater();
-  if (!isTauri) return null;
+/**
+ * A Linux package install is updated with its package manager (the in-app
+ * updater can't write to /usr/bin): the command, Copy and a download link.
+ */
+function PackageUpdate({ help }: { help: NonNullable<ReturnType<typeof packageUpdateHelp>> }) {
+  const [copied, setCopied] = useState<'no' | 'yes' | 'failed'>('no');
+  const copy = () => {
+    const text = help.command ?? '';
+    if (!navigator.clipboard) {
+      copyToClipboard(text);
+      setCopied('yes');
+      return;
+    }
+    navigator.clipboard.writeText(text).then(
+      () => setCopied('yes'),
+      () => setCopied('failed'),
+    );
+  };
+  let copyLabel = 'Copy command';
+  if (copied === 'yes') copyLabel = 'Copied';
+  else if (copied === 'failed') copyLabel = 'Copy failed: select it above';
+  return (
+    <Box direction="Column" gap="200">
+      <Text size="T200">
+        Lotus Chat was installed as a system package, so update it the same way
+        {help.command ? ' (your chats and settings are kept):' : '.'}
+      </Text>
+      {help.command && (
+        <Text
+          size="T200"
+          style={{ fontFamily: 'monospace', wordBreak: 'break-all', userSelect: 'all' }}
+        >
+          {help.command}
+        </Text>
+      )}
+      <Box gap="200" wrap="Wrap">
+        {help.command && (
+          <Button size="300" radii="300" variant="Secondary" onClick={copy}>
+            <Text size="B300">{copyLabel}</Text>
+          </Button>
+        )}
+        <Button
+          size="300"
+          radii="300"
+          variant="Secondary"
+          fill="None"
+          outlined
+          onClick={() => window.open(help.url, '_blank')}
+        >
+          <Text size="B300">{help.download}</Text>
+        </Button>
+      </Box>
+    </Box>
+  );
+}
 
-  const description =
-    status.state === 'checking'
+function AppUpdates() {
+  const { isTauri, status, check, install, installKind } = useTauriUpdater();
+  if (!isTauri) return null;
+  const packageHelp = packageUpdateHelp(installKind);
+  const packageUpdate =
+    !!packageHelp &&
+    (status.state === 'available' ||
+      (status.state === 'error' && isPackageManagedError(status.message)));
+
+  const description = packageUpdate
+    ? status.state === 'available'
+      ? `Update available: v${status.version}`
+      : 'An update is available.'
+    : status.state === 'checking'
       ? 'Checking for updates...'
       : status.state === 'up-to-date'
         ? 'Lotus Chat is up to date.'
@@ -2816,43 +2886,43 @@ function AppUpdates() {
     else check();
   };
 
-  const after =
-    status.state === 'available' ? (
-      <Button size="300" radii="300" onClick={() => install()}>
-        <Text size="B300">Install &amp; Restart</Text>
+  const after = packageUpdate ? undefined : status.state === 'available' ? (
+    <Button size="300" radii="300" onClick={() => install()}>
+      <Text size="B300">Install &amp; Restart</Text>
+    </Button>
+  ) : status.state === 'checking' || status.state === 'installing' ? (
+    <Spinner variant="Secondary" size="200" />
+  ) : status.state === 'error' ? (
+    <Box gap="200" wrap="Wrap" justifyContent="End">
+      <Button size="300" radii="300" variant="Secondary" onClick={retry}>
+        <Text size="B300">Try again</Text>
       </Button>
-    ) : status.state === 'checking' || status.state === 'installing' ? (
-      <Spinner variant="Secondary" size="200" />
-    ) : status.state === 'error' ? (
-      <Box gap="200" wrap="Wrap" justifyContent="End">
-        <Button size="300" radii="300" variant="Secondary" onClick={retry}>
-          <Text size="B300">Try again</Text>
+      {status.phase !== 'check' && (
+        <Button
+          size="300"
+          radii="300"
+          variant="Secondary"
+          fill="None"
+          outlined
+          onClick={() => window.open(manualDownloadUrl(navigator.userAgent), '_blank')}
+        >
+          <Text size="B300">Download installer</Text>
         </Button>
-        {status.phase !== 'check' && (
-          <Button
-            size="300"
-            radii="300"
-            variant="Secondary"
-            fill="None"
-            outlined
-            onClick={() => window.open(manualDownloadUrl(navigator.userAgent), '_blank')}
-          >
-            <Text size="B300">Download installer</Text>
-          </Button>
-        )}
-      </Box>
-    ) : (
-      <Button size="300" radii="300" variant="Secondary" onClick={check}>
-        <Text size="B300">Check</Text>
-      </Button>
-    );
+      )}
+    </Box>
+  ) : (
+    <Button size="300" radii="300" variant="Secondary" onClick={check}>
+      <Text size="B300">Check</Text>
+    </Button>
+  );
 
   return (
     <Box direction="Column" gap="100">
       <Text size="L400">App Updates</Text>
       <SequenceCard className={SequenceCardStyle} variant="SurfaceVariant" direction="Column">
         <SettingTile title="Check for Updates" description={description} after={after} />
-        {status.state === 'error' && (
+        {packageUpdate && packageHelp && <PackageUpdate help={packageHelp} />}
+        {status.state === 'error' && !packageUpdate && (
           <Text size="T200" priority="300" style={{ wordBreak: 'break-word' }}>
             Details: {status.message}
           </Text>