feat: panel refinements - toggles, no WCs, persistence

[auniverseaway]

• Remove Lit-based nx-panel block (panel.js/panel.css) in favor of
  utils/panel.js with plain DOM createPanel/showPanel/hidePanel functions
• Move panel styles from shadow DOM CSS to global styles.css
• Add action-button block to toggle before/after panels via fragments
• Extract api.js with daFetch (auth-aware), ping, source, list, signout
• Rewrite utils.js: environment-aware DA service origins via getEnv,
  improved parseWindowPath (returns null for invalid, strips /index)
• CSS: replace JS-added classes (spectrum-edge, app-frame) with
  meta-content attribute selectors
• Simplify profile color scheme toggle, import signout from api.js
• Add unit tests for utils (parseWindowPath, getEnv, loadStyle) and
  test mocks (IMS, CSS)
• Panel-aware default-content max-width when side panels are visible

Co-Authored-By: Claude Opus 4.6 (1M context) noreply@anthropic.com

Panels

https://nx2fixes--da-nx--adobe.aem.page/drafts/cmillar/panels

DA.LIVE prod + this NX2 PR + NX1

https://main--da-live--adobe.aem.live/?nx=nx2fixes
Expectation: this works E2E

DA.LIVE stage + this NX2 PR + NX2

https://dasites--da-live--adobe.aem.page/?nx=nx2fixes&nxver=2
Expectation: only da homepage works, but is correctly styled

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Commits

• a07f07d ✅ (latest)
• f384ff4 ✅

[auniverseaway]

@hannessolo I really love the approach to panels. Two things about this PR:

1. I made some small tweaks to the panel implementation...
   1. You can trigger by link (i.e. button)
   2. I think this is a base-level feature, so moved the styles into styles.css.
   3. I moved us away from the web component as it seemed a bit redundant and I'm worried that we'll get into shadow dom query selector hell later down the road.
2. I'm combining this my other relatively foundational PR. I removed the unrelated changes. This is now only the updates required for the panels.

Hopefully this works for you!

[auniverseaway]

Some non-critical open questions / comments:

We could easily ditch the fragments in favor of just loading a block directly. We would lose flexibility in that we could associate different blocks in authoring without a release, but I'm not sure we would actually use this. We may want to slice this differently anyway...

It seems like we pretty much know what we want each panel to always be:

1. left panel - chat
2. right panel - auxilary features (browse, recents, etc.)

I think this is good for now. Later down the road we may want to allow different views to determine what panels they get. This will be especially true if the auxilery panel becomes a nightmare to support.

[hannessolo]

I don't think these should be so hard-coded.

Maybe instead we should use the link in the button as the fragment path, something like /path/to/fragment#_open=panelBefore

[auniverseaway]

I think we're wondering the same thing, then. Let's do this:

We ditch the forced fragment abstraction. You supply a path to a block. If you want a fragment, the block you link to can provide it. Then in action button it is:

/tools/widgets/panel#_before=chat

Which means /blocks/chat/chat.js.

We could optionally support either now or later:

/tools/widgets/panel#_before=/fragments/panels/left

And if we run across a path that has fragments in it, we know to automatically use the fragment.js block.

[hannessolo]

This is working in the assumption that we can have multiple panels before/after. That was part of Kilian's design (think power users wanting to have 2 panels open) but I'm not 100% sure we should support it or not.

Based on your button impl, it seems we might only want to support 1 panel each side - in which case this code could be simplified.

[auniverseaway]

Yeah, I just told Claude to remove the WC piece, so I'm not sure what all is plumbed in there.

I do think we only allow three panels max, and for now, it's only one on each side.