feat: add WordPress Playground marketing blueprint

[chubes4]

Summary

Add a public WordPress Playground blueprint at blueprints/playground.json that opens a fresh, configured Data Machine in the visitor's browser with one click. The badge at the top of the README links to it. This is purely a marketing/onboarding surface — visitors get to try Data Machine without installing WordPress, configuring a server, or setting up plugins.

What the blueprint installs

Plugin	Source	Why
Agents API	git:directory from Automattic/agents-api@main	DM's substrate dependency. Already validated in the world-of-wordpress Playground.
AI Provider for OpenAI	git:directory from WordPress/ai-provider-for-openai@trunk	DM's chat/pipeline AI path. Already validated.
Data Machine	releases/latest/download/data-machine.zip	The star. Uses the vendor-bundled release asset shipped by the homeboy release workflow on every release.

After install the visitor is auto-logged-in as admin and dropped on /wp-admin/admin.php?page=datamachine-agent (the Agents page, which is DM's first-position admin menu entry) so the create-agent flow is the most direct path from "what is this?" to "I made it do something."

What's intentionally excluded

• Markdown Database Integration. DM's activation is dbDelta-based and works on Playground's native SQLite without MDI. MDI is a separate sell that deserves its own blueprint if/when we want to demo the markdown-as-DB story.
• Data Machine Code. DMC is a coding-agent extension. A DM-first marketing demo should be DM-first; a DMC-focused blueprint can be a follow-up PR once we know the DMC story we want to tell.
• Embedded demo agent/bundle. No pre-installed agent. Visitors land in DM with the create-agent wizard available. Honest framing — "here is the tool, build something" — and zero artifacts to maintain. A demo bundle can come in a follow-up PR once the blueprint shape is proven.

Validation

• python3 -c \"import json; json.load(open('blueprints/playground.json'))\" passes.
• Plugin install pattern (Agents API + AI Provider via git:directory, DM via releases/latest/download/*.zip) is identical to the world-of-wordpress blueprint, which has been booting successfully for the entire run of that experiment.
• DM v0.43.0 ZIP attached to the latest release (verified manually); the homeboy release-asset.yml workflow re-publishes a fresh ZIP on every future release via release.published, so the badge URL automatically tracks new versions.
• DM activation (datamachine_activate_plugin) only depends on dbDelta table creation and memory file scaffolding. Confirmed no MDI hard dependency.

Marketing value

• Repository visitors get a working trial in 10-20 seconds with zero local setup.
• The badge is a recognizable WordPress Playground pattern; visitors already know what it means.
• A Playground tab is a low-commitment way to evaluate DM. Lower bar than reading docs or watching a demo video.
• Once visitors are inside, the React admin UI, agent wizard, pipeline builder, and chat surface speak for themselves.

Follow-up ideas (not in this PR)

• Pre-installed simple example agent so visitors can hit Run on something without writing it themselves.
• DMC-focused blueprint that adds workspace + GitHub tools to the demo.
• Full agent-stack blueprint matching world-of-wordpress for visitors who want to see the whole brain.
• An empty pipeline shape pre-seeded into the create-agent wizard so the first-click is even faster.

AI assistance

• AI assistance: Yes
• Tool(s): Claude Code (Sonnet 4.5)
• Used for: Identified the gap during a Discord conversation, surveyed DM's admin menu registration to pick the right landingPage slug, surveyed DM's activation hook to confirm no MDI dependency, and drafted the blueprint, README badge, and PR description. Chris confirmed the stack scope (DM + Agents API + AI Provider, no MDI, no DMC) and the choice to ship an empty DM rather than a pre-installed example bundle.

[homeboy-ci]

Homeboy Results — data-machine

Lint

✅ lint — passed

Deep dive: homeboy lint data-machine --changed-since d69fae3

Test

✅ test — passed

ℹ️ No impacted tests found for --changed-since d69fae3
ℹ️ Run full suite if needed: homeboy test data-machine
Deep dive: homeboy test data-machine --changed-since d69fae3

Audit

✅ audit — passed

Deep dive: homeboy audit data-machine --changed-since d69fae3

Tooling versions

• Homeboy CLI: homeboy 0.182.0+56f7d298
• Extension: wordpress from https://github.com/Extra-Chill/homeboy-extensions
• Extension revision: 9eb4c10
• Action: unknown@unknown