chore: Add basic yarn-project CLAUDE.md (#17088)

I asked him and he said to do so :-P

---

> Should I commit CLAUDE.md to version control?

Yes, you should commit CLAUDE.md to version control. It contains useful
development commands and workflow information that would benefit other
developers
working on the project. Having this documentation in the repository
ensures:

  1. Other team members can reference the same commands
  2. The documentation stays in sync with the project
  3. Changes to development workflows can be tracked and reviewed

This is standard practice for project documentation that helps with
development setup and common tasks.

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
+```