fix: recover model-backed NPC chat

[JOY (JOY)]

Summary

• Recover model-backed NPC chat when DOS.AI returns plain speech or explicit say: text instead of strict JSON.
• Keep server-side validation intact: normalized model speech can only become action=say, then still passes the existing allowed-action validator.
• Smooth Unity chat mode status/animation behavior so focused NPCs keep dialog visuals, stop autonomous queue status spam, and show failed response feedback when model speech is suppressed.
• Tighten the UGUI chat panel so player messages stay left-aligned and bubbles size closer to message text.
• Lower the local example DOS.AI decision timeout to 30 seconds for faster dev feedback.

Root Cause

• Local dev AI budget had been exhausted, causing dos_ai_rate_limited fallback until the local budget storage was reset.
• After budget reset, DOS.AI was reachable, but valid natural-language model responses such as plain prose or say: "..." were rejected by the strict JSON parser.
• Unity dialog focus was racing with autonomous NPC status updates, making chat-mode NPCs show stale queued or dialog states.

Local Code Review Fallback

Verdict: APPROVED.

• Hard Rule feat(backend): add Nakama OSS local base #2 remains satisfied: LLM output still cannot mutate authoritative game state.
• Hard Rule feat(controller): add Simple KCC controller base #3 remains satisfied: Unity receives no model API keys; calls still go through Nakama.
• No ADR references were found in the touched files, so ADR compliance was checked against AGENTS.md project rules and existing code boundaries.
• Residual note: the current UGUI chat panel is still prototype-grade and should later move to prefab-driven UI styling, but this patch does not make that worse.

Verification

• npm.cmd run build in backend/nakama
• npm.cmd test in backend/nakama
• dotnet build Unity\SecondSpawn.AI.csproj
• dotnet build Unity\SecondSpawn.UI.csproj
• git diff --check --cached
• Staged-file em-dash scan
• Live local smoke: secondspawn_agent_decide returned source=model, action=say, HTTP 200 after Nakama restart
• Unity play smoke by JOY: NPC answered in the chat panel after the model-output recovery

Notes

Unrelated dirty files were intentionally left out of this PR: Photon generated code, generated knowledge packs, MCP research notes, and local private config.