feat(server): improve context management (#15448)

#### PR Dependency Tree


* **PR #15448** 👈

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

* **New Features**
* Added workspace artifact upload, browsing, removal, deduplication, and
library ownership support.
* Copilot now supports scoped document and artifact search, canvas
reading, live editor context, and frontend tools.
* Added scope and focus selectors with source-resolution receipts in
chat.
* Added embedding health, progress, synchronization, and retrieval
capabilities.
* Added BYOK policy visibility, provider restrictions, endpoint dialect
selection, and validation.
* Added delegated editor interactions and userdata document
authorization.

* **Bug Fixes**
* Improved attachment handling, cancellation, access control, retrieval
fallbacks, workspace synchronization, and configuration validation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

tests/affine-cloud-copilot/runtime-config.json

@@ -0,0 +1,21 @@
+{
+  "storages": {
+    "blob.storage": {
+      "provider": "assetpack",
+      "bucket": "blobs",
+      "config": {
+        "path": "/tmp/affine-cloud-copilot-storage"
+      }
+    }
+  },
+  "copilot": {
+    "enabled": true,
+    "storage": {
+      "provider": "assetpack",
+      "bucket": "copilot",
+      "config": {
+        "path": "/tmp/affine-cloud-copilot-storage"
+      }
+    }
+  }
+}