Bundle UnityToolkit for the TSC 1.3.9 beta release

[Tylevo]

TSC previously required the official UnityToolkit download followed by a separate SPT 4.1 compatibility overlay. This change bundles the complete UnityToolkit 2.0.1 dependency in the v1.3.9 ZIP with Arys's explicit permission, full license notices, and fixed path, length, and SHA-256 checks. WTT stays separately required; Fika stays optional.

Validation:

• 238 C# regression checks and 7 dashboard interaction tests passed; the full build passed with deployment disabled.
• Package validation checks the 186-file layout: 18 DLLs (4 TSC and 14 Toolkit/companion DLLs) and 8 bundles, including dependency tampering and missing-file cases.
• Static inspection of the official SPT 4.1.5 prepatch DLL confirms the same major/minor version rule as 4.1.4. It accepts the rebuilt Toolkit reference; this is not a 4.1.5 gameplay test.

Current Fika multiplayer and full SPT 4.1.5 gameplay remain untested. See the release notes and validation record.