docs: define alpha animation system architecture

[JOY (JOY)]

Summary

• Add the alpha animation system architecture decision doc.
• Decide that SECOND SPAWN should keep a project-owned semantic animation intent/profile layer as the source of truth.
• Keep ExplosiveLLC as a prototype adapter and clip source, keep Opsive UCC as a later Fusion-authority spike, and defer BR200-style custom Playables until measured evidence requires it.
• Link the new animation architecture from GitBook summary, systems index, architecture, decision register, body compatibility protocol, and roadmap.
• Create follow-up backlog issue [Animation] Data-driven body, weapon, and timing profile registry #278 for data-driven body, weapon, and timing profiles.

Verification

• git diff --check
• tools/windows/check-backlog-sync.ps1
• Local markdown link scan for modified docs
• Local code-review fallback: approved, docs-only change, no Unity package/scene/prefab mutation, no backend or authority boundary violation.

Research sources used

• Unity Humanoid retargeting, Animator Override Controller, and Animation Rigging docs.
• Photon Fusion animation concepts, Animations technical sample, and BR200 player docs.
• ExplosiveLLC RPG Character Mecanim Animation Pack ReadMe.
• Opsive UCC abilities, Animator Controller, and Animator Motion docs.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Keep combat authority on Fusion

This row makes Nakama an allowed owner for combat range, hit windows, damage, and death in the alpha source-of-truth animation doc. That contradicts the repo's backend boundary that Photon Fusion remains authoritative for in-zone combat and that Fusion validates combat intents before BodyTime or other state changes; following this table would let a prototype implement damage/death in Nakama and later diverge from the server-authoritative architecture.

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[chatgpt-codex-connector]

Match required actions to the enum

This makes DialogIdle and Listen required alpha actions, but the current CharacterActionId contract only has Talk, Agree, and Disagree for dialogue and no entries for those two ids. Because this same doc later says to freeze CharacterActionId as the semantic contract, the next profile validation or missing-action smoke work will either fail against nonexistent ids or invent untracked names; please either add the enum entries or keep the required list to the ids that actually exist.

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