Add wp-env setup for this repo

[MaggieCabrera]

Adds a local development environment powered by wp-env. All themes in the repo are available out of the box.

• Auto-detects a free port starting from 8888, avoiding conflicts with other services
• --theme <slug> activates a theme after startup; if the environment is already running, it skips startup
  and just switches the active theme
• env:stop and env:destroy read the saved port from .wp-env-port to always target the correct instance
• Theme activation is verified against WP-CLI output. A success message is only shown when the theme was
  actually switched

How to test

1. Fresh start
   npm run env:start -- --theme blue-note

• Visit http://localhost:8888, log in (admin / password)
• Confirm Blue Note is the active theme

2. Switch theme on a running env
   npm run env:start -- --theme archivist

• Should skip startup, just switch the theme
• Confirm Archivist is now active (no restart required)

3. Invalid theme slug
   npm run env:start -- --theme this-does-not-exist

• Should print an error and exit with a non-zero code
• Should NOT show a success message

4. Start with no theme flag
   npm run env:stop
   npm run env:start

• Should start normally, no theme activation step

5. Stop and restart with a different theme
   npm run env:stop
   npm run env:start -- --theme blue-note

• Should start the existing environment (not create a new one)
• Confirm Blue Note is active at http://localhost:8888

6. Destroy
   npm run env:destroy

• Containers and volumes removed, .wp-env-port file deleted
• Running npm run env:start after this should boot a clean instance

[MaggieCabrera]

Atlas needs TT3 as a dependency

[mikachan]

When I ran npm run env:start -- --theme blue-note, the env started fine, and I saw this success:

But it tried to activate Twenty Twenty-Five instead, which doesn't exist here. I could still manually switch to Blue Note afterwards, which worked fine.

And when I stopped the env and then ran npm run env:start -- --theme archivist, I saw the same success message again:

But Blue Note was still active.

Otherwise, the test environment is working well for me.

[mikachan]

These port checks are called for env:start, but we don't use anything similar for env:stop or env:destroy. Should the port that's being used be checked for these commands? I'm wondering if wp-env might accidentally stop or destroy the wrong instance if it hasn't checked the port.

[MaggieCabrera]

I think this whole thing might be more trouble than anything, I'll see what I can do

[MaggieCabrera]

I'm making it so that we store the active port in a file, and if we re run the env with a new theme it just changes it instead of destroying it/starting a new one again.

[mikachan]

Running npm run env:start -- --theme blue-note is working well for me now. Thanks! 🚢