fix: resend connectionStatus at staggered delays to prevent stuck loading screen on slow networks

The webview only leaves its initial loading screen once it receives a
connectionStatus=connected postMessage. VS Code drops postMessage calls made
before the webview's acquireVsCodeApi bridge is ready, so on slow/remote
networks the single send in _sendCachedState() can be lost forever, leaving
the sidebar stuck on #initial-loading.

Re-send connectionStatus at staggered delays (0.5s-20s) when connected, in
ChatViewProvider, AgentManagerPanelProvider and SessionEditorPanelProvider.
Stops automatically when the view/panel is disposed or replaced. Message is
idempotent.

Fixes #2996

packages/vscode/package.json

@@ -2,7 +2,7 @@
   "name": "openchamber",
   "displayName": "OpenChamber",
   "description": "%extension.description%",
-  "version": "1.19.0",
+  "version": "1.19.1",
   "publisher": "fedaykindev",
   "private": true,
   "repository": {
@@ -252,4 +252,4 @@
     "react-dom": "^19.1.1",
     "yaml": "^2.8.1"
   }
-}
+}