feat(unity): add BodyTime reincarnation debug loop

[JOY (JOY)]

Summary

• Adds a Unity prototype BodyTime and reincarnation debug panel on _AgentGateway.
• Surfaces lifecycle, SECOND balance, and reincarnation count on networked player state and HUD.
• Wires Unity profile refresh, BodyTime event, and reincarnation calls through Nakama.
• Adds a guarded local-only Nakama debug drain source for forcing zero BodyTime during Play Mode smoke.
• Binds the hub prototype NPC to its own actor profile and records the future server-authoritative time-loot rule in docs.

Verification

• npm run build && npm test in backend/nakama
• go test -count=1 ./... && go vet ./... in backend/gateway
• dotnet build SecondSpawn.AI.csproj --no-restore
• dotnet build SecondSpawn.UI.csproj --no-restore
• markdownlint-cli2
• git diff --check
• em/en dash scan

Unity Smoke Note

Unity compile passed through generated C# projects. MCP console was clean after clearing old Fusion CodeGen entries, but the MCP session stopped answering after a Play Mode command, so interactive Play Mode smoke is still blocked by the Unity MCP bridge rather than a compile error.

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[JOY (JOY)]

Local code-review fallback after implementation:

Scope reviewed:

• Unity BodyTime/reincarnation debug panel and scene wiring
• NetworkPlayer/HUD profile state surfacing
• CharacterMemorySync Nakama BodyTime and reincarnation calls
• Nakama guarded debug drain source and tests
• GDD/roadmap time-loot note

Findings:

• No blocking issues found.
• Server-authoritative boundary is preserved: normal BodyTime event sources remain allowlisted, and the fatal drain source only works when SECOND_SPAWN_ENABLE_DEBUG_BODYTIME=true in Nakama runtime env.
• Time/SECOND loot from other users is recorded as a future server-validated combat or zone-event rule, not implemented as client self-reporting.
• Unity C# compile passed through generated projects. MCP Play Mode smoke is still blocked because the MCP bridge stopped answering after a Play Mode command, not because of a compile failure.

Verification:

• npm run build && npm test in backend/nakama
• go test -count=1 ./... && go vet ./... in backend/gateway
• dotnet build SecondSpawn.AI.csproj --no-restore
• dotnet build SecondSpawn.UI.csproj --no-restore
• markdownlint-cli2
• git diff --check
• em/en dash scan
• GitHub checks are green

Verdict: APPROVED for merge into dev.