perf: code-split xterm bundle and gate terminal features for cloud (#8528)

## Summary

Code-splits the ~400KB xterm bundle and excludes terminal features from
cloud distribution where they are not needed.

### Changes

- **bottomPanelStore.ts**: Gate terminal tab registration behind
`__DISTRIBUTION__ !== 'cloud'` check with dynamic import, enabling
tree-shaking
- **keybindingService.ts**: Skip logs-terminal keybinding registration
for cloud distribution
- **vite.config.mts**: Add `vendor-xterm` code splitting group

### Bundle Impact

| Distribution | xterm in bundle | Terminal tabs |
|--------------|-----------------|---------------|
| cloud | ❌ No (~400KB saved) | None |
| localhost | ✅ Yes (vendor-xterm chunk) | Logs terminal |
| desktop | ✅ Yes (vendor-xterm chunk) | Logs + Command terminal |

### Verification Script

Run locally to verify xterm exclusion works correctly:

```bash
#!/bin/bash
set -e

echo "=== Verifying xterm bundle exclusion ==="
echo

# Clear Nx cache to ensure fresh builds
pnpm nx reset 2>/dev/null

# Build cloud distribution
echo "Building CLOUD distribution..."
rm -rf dist
DISTRIBUTION=cloud pnpm build --mode production 2>/dev/null

echo "Cloud build - checking for xterm:"
if grep -r "xterm" dist/assets/*.js >/dev/null 2>&1; then
  echo "  ❌ FAIL: xterm found in cloud bundle"
  grep -l "xterm" dist/assets/*.js | head -5
else
  echo "  ✅ PASS: xterm NOT in cloud bundle"
fi
echo

# Build localhost distribution
echo "Building LOCALHOST distribution..."
pnpm nx reset 2>/dev/null
rm -rf dist
DISTRIBUTION=localhost pnpm build --mode production 2>/dev/null

echo "Localhost build - checking for xterm:"
if grep -r "xterm" dist/assets/*.js >/dev/null 2>&1; then
  echo "  ✅ PASS: xterm found in localhost bundle"
  echo "  Files containing xterm:"
  grep -l "xterm" dist/assets/*.js | while read f; do
    size=$(wc -c < "$f")
    echo "    $(basename $f) ($(numfmt --to=iec $size))"
  done
else
  echo "  ❌ FAIL: xterm NOT in localhost bundle"
fi
echo

echo "=== Verification complete ==="
```

**Note**: Nx cache must be reset between builds with different
`DISTRIBUTION` values or it may return stale results.

## Test Plan

- [x] Quality gates pass (typecheck, lint, format, tests)
- [x] Cloud build verified: xterm NOT present
- [x] Localhost build verified: xterm present as vendor-xterm chunk

Fixes COM-14129

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-8528-perf-code-split-xterm-bundle-and-gate-terminal-features-for-cloud-2fa6d73d365081a093ecc74ca7ce6e7c)
by [Unito](https://www.unito.io)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
* Terminal tab declarations adjusted (no user-visible behavior change).
* Bottom panel tabs now load asynchronously; panel toggle falls back to
shortcuts when terminal tabs aren’t loaded.

* **Chores**
* Terminal tabs and related keybindings suppressed in cloud deployments.
  * Core commands wired to a new utility to support widget promotion.

* **Tests**
* E2E tests updated to handle async terminal-tab loading and minor test
cleanup.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: GitHub Action <action@github.com>
Co-authored-by: Alexander Brown <drjkl@comfy.org>

browser_tests/tests/bottomPanelShortcuts.spec.ts

@@ -113,21 +113,45 @@ test.describe('Bottom Panel Shortcuts', { tag: '@ui' }, () => {
     expect(hasModifiers).toBeTruthy()
   })
 
-  test('should maintain panel state when switching to terminal', async ({
+  test('should maintain panel state when switching between panels', async ({
     comfyPage
   }) => {
     const { bottomPanel } = comfyPage
 
+    // Open shortcuts panel first
     await bottomPanel.keyboardShortcutsButton.click()
     await expect(bottomPanel.root).toBeVisible()
-
-    await bottomPanel.toggleButton.click()
-    await expect(bottomPanel.root).toBeVisible()
-
-    await bottomPanel.keyboardShortcutsButton.click()
     await expect(
       comfyPage.page.locator('[id*="tab_shortcuts-essentials"]')
     ).toBeVisible()
+
+    // Try to open terminal panel - may show terminal OR close shortcuts
+    // depending on whether terminal tabs have loaded (async loading)
+    await bottomPanel.toggleButton.click()
+
+    // Check if terminal tabs loaded (Logs tab visible) or fell back to shortcuts toggle
+    const logsTab = comfyPage.page.getByRole('tab', { name: /Logs/i })
+    const hasTerminalTabs = await logsTab.isVisible().catch(() => false)
+
+    if (hasTerminalTabs) {
+      // Terminal panel is visible - verify we can switch back to shortcuts
+      await expect(bottomPanel.root).toBeVisible()
+
+      // Switch back to shortcuts
+      await bottomPanel.keyboardShortcutsButton.click()
+
+      // Should show shortcuts content again
+      await expect(
+        comfyPage.page.locator('[id*="tab_shortcuts-essentials"]')
+      ).toBeVisible()
+    } else {
+      // Terminal tabs not loaded - button toggled shortcuts off, reopen for verification
+      await bottomPanel.keyboardShortcutsButton.click()
+      await expect(bottomPanel.root).toBeVisible()
+      await expect(
+        comfyPage.page.locator('[id*="tab_shortcuts-essentials"]')
+      ).toBeVisible()
+    }
   })
 
   test('should handle keyboard navigation', async ({ comfyPage }) => {

browser_tests/tests/menu.spec.ts

@@ -107,7 +107,6 @@ test.describe('Menu', { tag: '@ui' }, () => {
       // Checkmark should be invisible initially (panel is hidden)
       await expect(checkmark).toHaveClass(/invisible/)
 
-      // Click Bottom Panel to toggle it on
       await bottomPanelItem.click()
 
       // Verify menu is still visible after clicking