Zoo-Topia: replayed on latest main (working runtime)

[samai-tai]

Replayed Zoo-Topia on top of upstream v0.1.2 and ported runtime hardening so local production build/start works. Includes multi-animal companions, settings, RIP wall portraits, and tests.

[iamlukethedev]

I don't think this PR should be merged as-is.

Two correctness issues block this for me:

1. server/gateway-proxy.js can still dereference upstreamWs when upstream setup never created a socket. In the current flow, startUpstream() can exit early with pendingUpstreamSetupError and leave upstreamWs null, but forwardConnectFrame() still ends with upstreamWs.send(...). This makes the connect path brittle when gateway settings are missing/invalid or upstream setup fails early.

2. agentFleetHydration.ts still derives the fallback defaultId by indexing back into rawAgents[index] after agents has already been compacted with flatMap(...). If any invalid hello-snapshot entries are skipped before the default one, the wrong agent can be chosen as default.

I’d want both fixed before merge, and I’d also like targeted coverage for:

• proxy connect behavior when upstream setup fails before upstreamWs exists,
• hello snapshot fallback when some health.agents entries are invalid/skipped but one later entry is marked isDefault.