feat: refactor upgrade routine and add v0.6.0 migrations

[justlevine]

What?

• Closes Rename plugin from “AI Experiments” to “AI” and define feature vs experiment classification #234 (for real this time)

This PR creates a new Upgrades routine to handle scalable plugin upgrades and data migrations. Additionally it:

• Creates the new WordPress/AI/Admin/Upgrades/V0_6_0 for migrating the ai_experiments_* => wpai_feature_* options changed in feat!: Refactor Experiments to be a type of Feature #316
• Refactors Migrations/Credential_Migration to Admin/Upgrades/V0_5_0.
• Adds an activation hook to trigger migrations on.

Why?

A central and future-compatible way to scale plugin upgrades.

How?

1. On plugin activation (or admin_init as a fallback), the Upgrades routine checks gets the db version, and checks if any Abstract_Upgrade classes need to run, by comparing it with the Abstract_Upgrade::$version
2. If the upgrade succeeds, the db version is upgraded to the Abstract_Upgrade::$version. If it fails, then the Upgrade routine stops and an admin notice is displayed.
3. One all Upgrade routines succeed, the latest plugin version is saved to the databse.

Todo

• Backfill tests.

Use of AI Tools

• Github Copilot autocomplete
• PHPUnit tests were backfilled by GPT 5.4 and then heavily deslopped.

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

[Copilot]

Pull request overview

Refactors the legacy credential migration into a versioned upgrade framework and introduces an activation-time upgrade trigger, with an additional v0.6.0 option rename migration.

Changes:

• Replaces the old Credential_Migration with a new Admin\Upgrades framework (Abstract_Upgrade, Upgrades, activation hook).
• Moves the v0.5.0 credential migration logic into Admin\Upgrades\V0_5_0 and updates integration tests accordingly.
• Adds a new v0.6.0 upgrade class to migrate ai_experiment_* options to wpai_* equivalents.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
tests/Integration/Includes/Migrations/Credential_MigrationTest.php	Updates integration tests to target the new V0_5_0 upgrade routine and version option key.
includes/bootstrap.php	Switches from direct migration call to Upgrades->init() and adds an activation hook to run upgrades.
includes/Migrations/Credential_Migration.php	Removes the legacy migration class (replaced by versioned upgrades).
includes/Admin/Upgrades/V0_5_0.php	Implements the v0.5.0 credential migration as an upgrade routine class.
includes/Admin/Upgrades/V0_6_0.php	Adds option migration logic for v0.6.0 (old ai_experiment_* → new wpai_*).
includes/Admin/Upgrades/Abstract_Upgrade.php	Introduces reusable base class for versioned upgrade routines with WP_Error reporting.
includes/Admin/Upgrades.php	Adds orchestrator that runs upgrade classes, stores DB version, and shows failure notice.
includes/Admin/Activation.php	Adds activation callback that triggers upgrades during plugin activation.

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[codecov]

Codecov Report

❌ Patch coverage is 82.75862% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 57.48%. Comparing base (561768c) to head (3c64c5d).
⚠️ Report is 30 commits behind head on develop.

Files with missing lines	Patch %	Lines
includes/Admin/Upgrades.php	82.05%	7 Missing ⚠️
includes/Admin/Upgrades/Abstract_Upgrade.php	66.66%	4 Missing ⚠️
includes/Admin/Activation.php	66.66%	1 Missing ⚠️
includes/Admin/Upgrades/V0_5_0.php	91.66%	1 Missing ⚠️
includes/Admin/Upgrades/V0_6_0.php	95.00%	1 Missing ⚠️
includes/bootstrap.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #321      +/-   ##
=============================================
+ Coverage      57.05%   57.48%   +0.42%     
- Complexity       591      610      +19     
=============================================
  Files             42       46       +4     
  Lines           3083     3147      +64     
=============================================
+ Hits            1759     1809      +50     
- Misses          1324     1338      +14     

Flag	Coverage Δ
unit	57.48% <82.75%> (+0.42%)	⬆️

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[github-actions]

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Co-authored-by: justlevine <justlevine@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>

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[justlevine]

Tests backfilled 🚀