refactor(core): move AppMenu component tree into core/src/appmenu/

[pringelmann]

Summary

Moves AppMenu (the waffle) out of core-main into its own core-appmenu chunk with a small bootstrap, loaded as a normal deferred core script. Drops the old MainMenu.js mount since the component now owns its entry point.

This ensures the waffle menu appears sooner, allowing users to switch apps before page content loads.

How this works

On master the menu mounts inside initCore(), which runs on DOMContentLoaded, so it only paints after the whole deferred-script queue (including the dashboard). The new chunk mounts at its own eval alongside unified-search, before DOMContentLoaded, so it shows up with the header instead of after the page finishes.

The videos below were recorded using Firefox's Good 3G network throttle profile to simulate a poor connection.

Before:

waffle_before.mp4

After:

waffle_after.mp4

Nothing changes for users, the menu renders the same.

Changes

• New core-appmenu webpack entry from core/src/appmenu/, pulled into core via addScript util.
• New bootstrap mounts AppMenu on its own and replaces the setUp() call in init.js.
• Removed core/src/components/MainMenu.js.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes (no visual change)
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 35.x)

[pringelmann]

/compile amend

[susnux]

How is this faster? Its so core-main where it was loaded previously is still loaded first.
Meaning its even is evaluated a bit later now because unified search and unsupported-browsers are evaluated before this script.

The only proper way to load this faster is to do an async loading which we already tried before but there we have the problem that the dependencies loaded in core-common need to be loaded which takes the most time.

[pringelmann]

How is this faster? Its so core-main where it was loaded previously is still loaded first. Meaning its even is evaluated a bit later now because unified search and unsupported-browsers are evaluated before this script.

The only proper way to load this faster is to do an async loading which we already tried before but there we have the problem that the dependencies loaded in core-common need to be loaded which takes the most time.

It's faster because the old mount was inside the DOMContentLoaded callback in initCore, so it waited for the whole deferred-script queue. The new standalone chunk mounts at its own eval, alongside unified-search, before DCL. No async or extra dependencies needed.

I will update the PR description explaining the actual mechanism in more detail.