docs: add ONBOARDING.md for new contributors

[JurijRevega]

Describe monorepo layout, local setup, env vars, common yarn commands, setup checks, troubleshooting, glossary, and where to read code first.

Summary by CodeRabbit

Release Notes

• Documentation
  • Added comprehensive onboarding documentation including repository architecture overview, local setup instructions, common development commands, troubleshooting guides, and terminology glossary.

[coderabbitai]

📝 Walkthrough

Walkthrough

A new ONBOARDING.MD documentation file has been added to the Excalidraw repository. This file provides comprehensive guidance on the Yarn workspaces monorepo architecture, including tech stack, environment setup, local installation steps, common root commands, troubleshooting resources, and a glossary of key terms.

Changes

Cohort / File(s)	Summary
Onboarding Documentation ONBOARDING.MD	New comprehensive onboarding guide covering monorepo architecture, tech stack, prerequisites, environment variable conventions, step-by-step setup instructions, common root commands, troubleshooting table, and glossary of key terms.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A guide for all who venture near,
Our monorepo structure crystal clear,
With workspaces arranged just right,
And setup steps that shine so bright! 🌟

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'docs: add ONBOARDING.md for new contributors' directly and accurately summarizes the main change: adding a documentation file for onboarding new contributors.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@ONBOARDING.MD`:
- Line 265: Update the stale "Last updated" timestamp in ONBOARDING.MD by
replacing the current line containing "**Last updated:** 2025-03-26" with the
current date (or the PR creation date) so the document reflects the most recent
update; locate the literal string "**Last updated:**" in the file and modify the
date portion accordingly.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d3e3717e-2c67-439e-a090-dd2262464d9a

📥 Commits

Reviewing files that changed from the base of the PR and between be47f1d and d328008.

📒 Files selected for processing (1)

• ONBOARDING.MD

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Update the stale “Last updated” date.

This timestamp is one year behind the PR creation date, which can make the doc look outdated even when content is current.

Suggested patch

-- **Last updated:** 2025-03-26
+- **Last updated:** 2026-03-26

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	- **Last updated:** 2025-03-26
	- **Last updated:** 2026-03-26

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@ONBOARDING.MD` at line 265, Update the stale "Last updated" timestamp in
ONBOARDING.MD by replacing the current line containing "**Last updated:**
2025-03-26" with the current date (or the PR creation date) so the document
reflects the most recent update; locate the literal string "**Last updated:**"
in the file and modify the date portion accordingly.