feat: add project requirements and user stories for Adiuva MVP

- Created prd.json with detailed user stories, acceptance criteria, and implementation notes for the Adiuva project.
- Updated progress.txt to reflect recent implementations of routers for checkpoints and notes, along with learnings for future iterations.
- Modified ralph.sh to change the default tool from "amp" to "claude" for improved compatibility.

.claude/.mcp.json

@@ -0,0 +1,12 @@
+{
+  "mcpServers": {
+    "playwright": {
+      "type": "stdio",
+      "command": "npx",
+      "args": [
+        "@playwright/mcp@latest"
+      ],
+      "env": {}
+    }
+  }
+}