docs: add CONTRIBUTING.md

[Arvuno]

Summary

Adds CONTRIBUTING.md

Testing

N/A

---

Summary by cubic

Adds CONTRIBUTING.md with quick local setup, dev commands, and PR steps for both python and node. Also adds internal docs (00_STATE.md, 01_REPO_MAP.md, 05_PR_CANDIDATES.md, 06_SELECTED_5_PR_PLAN.md) covering repo state, file map, defects, and a short PR plan to guide contributors.

^{Written for commit d17802f. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

1 issue found across 5 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="00_STATE.md">

<violation number="1" location="00_STATE.md:1">
P2: Wrong file committed: PR aims to add CONTRIBUTING.md but commits 00_STATE.md (internal repository analysis) instead.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Fix all with cubic | Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Wrong file committed: PR aims to add CONTRIBUTING.md but commits 00_STATE.md (internal repository analysis) instead.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At 00_STATE.md, line 1:

<comment>Wrong file committed: PR aims to add CONTRIBUTING.md but commits 00_STATE.md (internal repository analysis) instead.</comment>

<file context>
@@ -0,0 +1,103 @@
+# 00_STATE.md — AgentMail Toolkit Analysis
+
+## Repository Overview
</file context>