fix: sync dev branch with main timeline/schema changes and remove stale providers

Forward-port main's timeline epoch tracking, projected window selection,
and schema updates into dev. Remove aider/amp/gemini providers and
provider-history-compatibility layers that are no longer needed.

package.json

@@ -69,8 +69,8 @@
     "get-port-cli": "^3.0.0",
     "knip": "^5.82.1",
     "patch-package": "^8.0.1",
-    "react": "19.1.4",
-    "react-dom": "19.1.4",
+    "react": "19.1.0",
+    "react-dom": "19.1.0",
     "typescript": "^5.9.3"
   },
   "description": "Paseo: voice-controlled development environment with OpenAI Realtime API",
@@ -94,8 +94,8 @@
   "license": "AGPL-3.0-or-later",
   "overrides": {
     "lightningcss": "1.30.1",
-    "react": "19.1.4",
-    "react-dom": "19.1.4"
+    "react": "19.1.0",
+    "react-dom": "19.1.0"
   },
   "dependencies": {
     "@anthropic-ai/claude-agent-sdk": "^0.2.11",