chore: add CLAUDE.md and project memory for Claude Code

Add CLAUDE.md with project guidance for adding new LLM providers.
Add .claude/memory/ with feedback rules:
- Preserve markdown quotes when editing
- Save memories in project directory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/settings.json

@@ -0,0 +1,7 @@
+{
+  "permissions": {
+    "allow": [
+      "Write(*.md)"
+    ]
+  }
+}