chore: move research notes to notes/ and add to gitignore

- Move SDD document to notes/
- Move sdk-research/ to notes/
- Move tapi-*.md files to notes/
- Move e2e-cli to notes/ (testing only)
- Add notes/ to .gitignore

These are working notes/research and should not be in version control.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abueide

.gitignore

@@ -97,3 +97,6 @@ packages/core/src/info.ts
 
 AGENTS.md
 
+# Notes and research (not for commit)
+notes/
+