docs: Create AGENTS.md

[charlesvien]

Split dev guide into AGENTS.md and reference docs

This is good to merge before refactor stuff, should help a little bit in the interim

[charlesvien]

• docs: Create AGENTS.md #2275 👈 (View in Graphite)
• main

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[greptile-apps]

T-Rex Logs

What T-Rex did

• Ran a package dry-run for packages/agent to inspect the files that would be published.
• Verified that packages/agent/package.json still declares CLAUDE.md in the published files list.
• Verified there is no package-local CLAUDE.md, and the dry-run tarball contains no CLAUDE.md entry.
• Verified the root CLAUDE.md symlink points to AGENTS.md, and noted that the root symlink is not part of the @posthog/agent publish output.

Artifacts

Package dry-run manifest for packages/agent

• Helps verify the contents of the published manifest for packages/agent and what would be included in the tarball.

_{Ran code and verified through T-Rex}

Comments Outside Diff (2)

1. apps/code/SCHEMA.md

   Preserve analytics catalog

   Deleting this file drops the analytics event catalog and the “Adding a new event” checklist, but the new docs only keep the naming rules. When someone adds a tracked event, they no longer have the canonical place that explains which catalog row to update and what each existing event means, so the analytics docs can drift from ANALYTICS_EVENTS even though this PR is meant to split the guide into reference docs.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: apps/code/SCHEMA.md
   Line: 86
   
   Comment:
   **Preserve analytics catalog**
   
   Deleting this file drops the analytics event catalog and the “Adding a new event” checklist, but the new docs only keep the naming rules. When someone adds a tracked event, they no longer have the canonical place that explains which catalog row to update and what each existing event means, so the analytics docs can drift from `ANALYTICS_EVENTS` even though this PR is meant to split the guide into reference docs.
   
   How can I resolve this? If you propose a fix, please make it concise.

2. packages/agent/package.json, line 147 (link)

   Declared doc not published

   packages/agent/package.json still whitelists CLAUDE.md, but no packages/agent/CLAUDE.md exists. The package dry-run succeeds silently and publishes a tarball without that file, so consumers of @posthog/agent will not receive the agent context file that the manifest still declares.

   Artifacts

   
   

   Package dry-run manifest showing no CLAUDE.md entry

   • Keeps the command output available without making the summary code-heavy.

   _{Ran code and verified through T-Rex}

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
apps/code/SCHEMA.md:86
**Preserve analytics catalog**

Deleting this file drops the analytics event catalog and the “Adding a new event” checklist, but the new docs only keep the naming rules. When someone adds a tracked event, they no longer have the canonical place that explains which catalog row to update and what each existing event means, so the analytics docs can drift from `ANALYTICS_EVENTS` even though this PR is meant to split the guide into reference docs.

_{Reviews (1): Last reviewed commit: "Update AGENTS.md" | Re-trigger Greptile}