chore: Add basic yarn-project CLAUDE.md

Author: spalladino

.gitignore

@@ -29,5 +29,4 @@ docs/.yarn/install-state.gz
 docs/docs/protocol-specs/public-vm/gen/
 
 # for those who use Claude Code
-CLAUDE.md
 .claude

yarn-project/CLAUDE.md

@@ -0,0 +1,74 @@
+# Aztec TypeScript Monorepo Development Commands
+
+## Project Structure
+- TypeScript monorepo with each folder being a package
+- Root directory: `yarn-project`
+
+## Compilation Commands
+
+### Full Project
+```bash
+yarn tsc -b
+```
+
+### Specific Package
+```bash
+cd <package-name>
+yarn tsc -b
+```
+
+## Testing Commands
+
+### Run Test File in Package
+```bash
+cd <package-name>
+yarn test FILENAME
+```
+
+### Run Specific Test
+```bash
+cd <package-name>
+yarn test FILENAME -t 'test-name'
+```
+
+### End-to-End Tests (Special Case)
+```bash
+cd end-to-end
+yarn test:e2e FILENAME
+```
+**IMPORTANT**: Never run more than one e2e test in parallel
+
+### Sequential Testing (for packages with port conflicts)
+Some packages (e.g., ethereum) must run tests sequentially due to service conflicts (anvil ports):
+```bash
+cd <package-name>
+yarn test --runInBand
+```
+
+## Logging During Tests
+Set `LOG_LEVEL` environment variable:
+```bash
+LOG_LEVEL=verbose yarn test FILENAME
+LOG_LEVEL=debug yarn test FILENAME
+```
+
+Available levels: trace, debug, verbose, info, warn (verbose recommended)
+
+Example:
+```bash
+cd aztec-node
+LOG_LEVEL=verbose yarn test some-test-file.test.ts
+```
+
+## Dependency Management
+After changing dependencies in any package.json:
+```bash
+yarn && yarn prepare
+```
+
+## Format and Lint
+Always run before committing:
+```bash
+yarn format
+yarn lint
+```