refactor: automatically migrate engine v1 projects - #2130

Forum: https://forum.playcanvas.com/t/important-playcanvas-editor-support-for-engine-v1-ends-on-july-1st/42242

Engine V1 projects now move to Engine V2 automatically when a user with write access opens them.

What's Changed

• Copies scene gamma correction and tone mapping to camera components, sets engineV2 to true, and reloads the Editor.
• Removes the manual Engine V1/V2 switch and its confirmation picker.
• Leaves WebGL 1, AudioSource, schema fields, inspectors, and other compatibility paths unchanged.

Rollout

Deploy this frontend first. Writable Engine V1 projects migrate when opened. Read-only sessions do not persist a migration; a user with write access or the later backend migration must update those projects.

Manual smoke test

1. Open a writable Engine V1 project with non-default scene gamma correction or tone mapping; expected: the camera values are updated, engineV2 becomes true, and the Editor reloads.
2. Open Settings > Engine; expected: the engine version selector remains, but the Engine V1/V2 switch is absent.
3. Open an existing Engine V2 project; expected: it opens without a migration or forced reload.
4. Open an Engine V1 project with read-only access; expected: no project or scene data is persisted.

Checks

• I confirm I have read the contributing guidelines