Studio Agents Suite: Add starter agents.md file and ship it to site root

[katinthehatsite]

Related issues

Fixes https://linear.app/a8c/issue/STU-1332/create-starter-agentsmd-template
Related to https://linear.app/a8c/issue/STU-1334/implement-auto-placement-of-agentsmd-in-site-root

Proposed Changes

This PR implements the AGENTS.md file to the root of Studio sites. The file includes guidance on Studio CLI commands and usage, WordPress development practices as well as SQLite database documentation.

Testing Instructions

• Pull the changes from this branch
• Start Studio with npm start
• Create a Studio site
• Navigate to the Overview tab and open the site in Finder
• Confirm that AGENTS.md file is present in the root of the site
• Next, open a Terminal and cd into the site
• Start, for example, Claude
• Ask Claude about the database integration
• Confirm that you get the answers related to SQLite database integration
• Ask Claude about Studio CLI commands
• Confirm that it gets answers based on the AGENTS.md file

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[katinthehatsite]

For now, we do not overwrite the file. We will consider some more flexibility here to make sure the users get the most recent versions of AGENTS.md shall we have to modify it. It will be solved under https://linear.app/a8c/issue/STU-1332/create-starter-agentsmd-template

[epeicher]

Thanks @katinthehatsite for adding that! I have reviewed the Agents.md and it looks great, we can iterate over it as we use it (if required) but it's a great starting point in my opinion.

have added a couple of comments for consideration, the main one about externalising the file, but interested in other points of view.

[epeicher]

Have we considered extracting this template to an external .md file for easier maintenance?

[katinthehatsite]

Yeah I initially did that :) Then, I went back on it but I think we will have to do it regardless based on my exploration in #2698

I will move it in that PR if that's okay so that I don't have to do another rebase 😅

[epeicher]

I will move it in that PR if that's okay so that I don't have to do another rebase

That's fine 👍

[epeicher]

I have been testing using Claude and Codex, and both agents work as expected, they see the Agents.md and allow to ask and do actions using natural language, like Please create a preview site

I am approving this as my comments are non-blocking

[wpmobilebot]

📊 Performance Test Results

Comparing 00f3022 vs trunk

site-editor

Metric	trunk	00f3022	Diff	Change
load	1768.00 ms	1761.00 ms	-7.00 ms	⚪ 0.0%

site-startup

Metric	trunk	00f3022	Diff	Change
siteCreation	6122.00 ms	7085.00 ms	+963.00 ms	🔴 15.7%
siteStartup	3934.00 ms	3935.00 ms	+1.00 ms	⚪ 0.0%

---

Results are median values from multiple test runs.

Legend: 🟢 Improvement (faster) | 🔴 Regression (slower) | ⚪ No change (<50ms diff)