fix: publish the plain OpenAdapt install path

[abrichr]

Summary

• replace the temporary browser-extra command with the plain pip install openadapt path across all public acquisition and template surfaces
• keep the historical installer browser argument compatible while installing the base package
• update the canonical release ledger to OpenAdapt 1.15.0 with the exact tag, parent commit, PyPI URLs, and hashes

Verification

• published OpenAdapt 1.15.0 installed in a new Python 3.12 environment
• the OpenAdapt quickstart returned VERIFIED in 5.2 seconds with 2 of 2 effects and 0 model calls
• 205 website tests passed
• the Next.js production build passed
• the live PyPI and GitHub version check passed
• the shell syntax check passed

[netlify]

✅ Deploy Preview for cosmic-klepon-3c693c ready!

Name	Link
🔨 Latest commit	b2c1d59
🔍 Latest deploy log	https://app.netlify.com/projects/cosmic-klepon-3c693c/deploys/6a8efd0caf270200084a9cc9
😎 Deploy Preview	https://deploy-preview-376--cosmic-klepon-3c693c.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
🤖 Make changes	Run an agent on this branch

---

To edit notification comments on pull requests, go to your Netlify project configuration.