fix(playerbots): initialize creature spawn instance fields

[Mathih13]

The full-world creature import adds instance_id and source_guid to Core's CreatureSpawn type. Ten playerbot fixtures construct that type directly and no longer compile.

Initialize both fields. Shared-world fixtures use Instance zero. The transfer destination fixture keeps its existing Instance ID. Each fixture uses source_guid = 0 because it creates the spawn directly.

Verified formatting, the Package API check and the all-Packages Wasm compile through .github/check-core-tip.sh against the paired Core branch. This change must land with Core PR #688.

Made with GPT-6 Astra through the Codex harness in T3 Code.

[Mathih13]

Merged with LyraCoreProject/LyraCore#688. The required Module check passed on 4c177ab18b1c84786ef525485c446f652bdc3802, and Core's final Official Packages check passed against the paired branch. The fixture changes initialize the new Creature Spawn Instance fields. Both PRs are now merged.