Draft: feat: migrate UXF to Unity 6 package v3.0.0

[jackbrookes]

Changelog

3.0.0

Unity 6 and package distribution

• Added the initial Unity Package Manager manifest and package-local agent/contributor guidance.
• Migrated the development project to Unity 6000.3.25f1 and moved UXF from Assets/UXF to the embedded Packages/com.immersivecognition.uxf package. The package declares Unity 6000.3, UGUI, Input System and UnityWebRequest dependencies.
• Added runtime, editor, EditMode and PlayMode assembly definitions; an importable UXF Examples Package Manager sample; package-local documentation; and a separate ci/consumer installation fixture.
• Added a versioned UPM ZIP and SHA-256 checksum workflow. Unity test jobs are available when licensing is configured; publishing requires those jobs to pass. Repository policy requires all development-project and clean-consumer EditMode and PlayMode tests to pass locally before merge.
• Moved example scenes to Samples~, converted their Standard and fire-particle materials to URP 17.3, and configured the development project's URP assets. The UXF runtime itself has no URP dependency. Example setup, StreamingAssets fixtures and WebGL template installation are documented separately.

Runtime and editor

• Added Input System support for UXF pointer, keyboard and UI components, including Input System-only consumers. The clean-consumer CI configuration now explicitly selects legacy or new input for each matrix job.
• Replaced Windows Forms/Ookii managed dialog DLLs with native Windows file/save dialogs and a Shell IFileOpenDialog folder picker. The folder picker uses an STA thread and guards against reentrant dialog calls.
• Updated WebGL string interop, Unity 6 API/version guards, build validation and editor controls. UI-free Sessions are checked at build time, and batchmode errors fail without a modal dialog.
• Improved FileSaver path validation, CSV quoting, culture isolation, relative path output, queue synchronization and cleanup. Session shutdown waits for queued tracker writes; known static state resets between play sessions.
• Removed the EasyEvent reflection patch and global reorderable inspector. The [UXF_Rig] Session is enabled by default, and edit-time validation no longer dirties scenes.

Upgrade notes and validation

• This is a breaking move from Assets/UXF to Package Manager. Follow the package README before importing examples or migrating an existing project; do not keep both copies installed.
• CSV quoting and relative paths changed, and the Windows-only SFB.WindowWrapper helper was removed. Review output consumers and custom dialog integrations before upgrading.
• Earlier local Unity 6 runs passed package and clean-consumer EditMode/PlayMode suites. The final Windows dialog flow, tagged installation, player builds, browser/device behavior and full sample walkthroughs remain open in the validation matrix. These earlier runs do not certify the final branch.