feat: cleanup chat panel (#14259)

#### PR Dependency Tree


* **PR #14258**
  * **PR #14259** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

* **Refactor**
* Split AI initialization into separate editor, app, and shared
registries; removed legacy chat-panel and replaced it with a
component-based editor chat, updating wiring and public exports.
* Propagated server/subscription/model services into chat/playground
components and improved session lifecycle and UI composition.

* **Tests**
* Added tests for AI effect registration and chat session resolution;
extended DOM/test utilities and assertions.

* **Chores**
  * Added happy-dom for runtime and test environments.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

yarn.lock

@@ -457,6 +457,7 @@ __metadata:
     fuse.js: "npm:^7.0.0"
     graphemer: "npm:^1.4.0"
     graphql: "npm:^16.9.0"
+    happy-dom: "npm:^20.3.0"
     history: "npm:^5.3.0"
     idb: "npm:^8.0.0"
     idb-keyval: "npm:^6.2.2"
@@ -18961,7 +18962,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@types/ws@npm:^8.0.0, @types/ws@npm:^8.5.10":
+"@types/ws@npm:^8.0.0, @types/ws@npm:^8.18.1, @types/ws@npm:^8.5.10":
   version: 8.18.1
   resolution: "@types/ws@npm:8.18.1"
   dependencies:
@@ -26694,14 +26695,16 @@ __metadata:
   languageName: node
   linkType: hard
 
-"happy-dom@npm:^20.0.0":
-  version: 20.0.7
-  resolution: "happy-dom@npm:20.0.7"
+"happy-dom@npm:^20.0.0, happy-dom@npm:^20.3.0":
+  version: 20.3.0
+  resolution: "happy-dom@npm:20.3.0"
   dependencies:
     "@types/node": "npm:^20.0.0"
     "@types/whatwg-mimetype": "npm:^3.0.2"
+    "@types/ws": "npm:^8.18.1"
     whatwg-mimetype: "npm:^3.0.0"
-  checksum: 10/1161bfe8fcac0fd093b8fbe8af29e8a6525437f17424be97b21401f0741e6473541b30b080066a32990b884eae4b83a1fd1f948a52607975bc98d1b90b394509
+    ws: "npm:^8.18.3"
+  checksum: 10/aade5560110eeaad502679a314f4d3b8658fe4697c1914d0de09ec6a176611ad0c8953f0aa559c56d1afabe0ab8465cde7b4811006df6eb3b54c5e5ea4169b29
   languageName: node
   linkType: hard
 
@@ -38868,9 +38871,9 @@ __metadata:
   languageName: node
   linkType: hard
 
-"ws@npm:^8.17.1, ws@npm:^8.18.0, ws@npm:^8.18.2":
-  version: 8.18.3
-  resolution: "ws@npm:8.18.3"
+"ws@npm:^8.17.1, ws@npm:^8.18.0, ws@npm:^8.18.2, ws@npm:^8.18.3":
+  version: 8.19.0
+  resolution: "ws@npm:8.19.0"
   peerDependencies:
     bufferutil: ^4.0.1
     utf-8-validate: ">=5.0.2"
@@ -38879,7 +38882,7 @@ __metadata:
       optional: true
     utf-8-validate:
       optional: true
-  checksum: 10/725964438d752f0ab0de582cd48d6eeada58d1511c3f613485b5598a83680bedac6187c765b0fe082e2d8cc4341fc57707c813ae780feee82d0c5efe6a4c61b6
+  checksum: 10/26e4901e93abaf73af9f26a93707c95b4845e91a7a347ec8c569e6e9be7f9df066f6c2b817b2d685544e208207898a750b78461e6e8d810c11a370771450c31b
   languageName: node
   linkType: hard