[StephenHodgson]

• skip license return on github hosted macos and linux runners
• bump unity-cli@v4.1.0
• retry-failed-jobs@v1 for reruns
• bump deps
• update ci workflows
• update readme

[Copilot]

🟡 Changes recommended

Unresolved issues can prevent floating lease returns and misclassify legacy Unity installations, while required third-party copyright notices are missing from the distribution.

2 open issues

• Resolve the actual Unity version for legacy license activation and return · New
• Always return floating licenses even when return-license is never · New

What changed in this PR

Prepares the Unity license activation action for v3, updating its licensing backend, license-return controls, and CI validation workflows.

Changes:

• Adopts unity-cli 4.1.0 with cached-license activation, retryable failure notices, and configurable license returns.
• Shares encrypted licenses across eligible CI jobs and adds automatic retries and artifact cleanup.
• Updates dependencies, action inputs, and migration documentation.

File	Description
src/​deactivate.ts	Adds return policies and professional-seat warnings.
src/​activate.ts	Uses new activation helpers, masks credentials, and reports retryable failures.
README.md	Documents v3 behavior, inputs, caching, and migration.
package.json	Bumps the action and unity-cli versions.
package-lock.json	Refreshes resolved dependencies.
dist/​licenses.txt	Updates bundled dependency notices.
action.yml	Adds return-license and deprecates license-version.
.github/​workflows/​validate.yml	Adds shared-license preparation, cleanup, and parallel validation.
.github/​workflows/​rerun-validate.yml	Retries failed validation jobs using failure markers.
.github/​workflows/​build.yml	Consumes encrypted licenses and updates Unity actions.

_{Review effort: Balanced}