Fix multiplayer remote damage feedback

[agustin-lowpoly]

Summary:

• Keep connected remote players visible when interpolation samples go stale instead of blinking out.
• Wire remote player damage events into pain animation state and local-attacker blood feedback.
• Add presenter regression coverage for remote damage handling.

Validation:

• node --test test/multiplayer/presentation.test.mjs
• pnpm build
• node bench/captureMultiplayerCombatProof.mjs
• e1m7 two-client idle visibility probe: hiddenSamples 0, missingSamples 0
• node test/browser/runMultiplayerBrowserSmoke.mjs --map e1m7 --duration-ms 4000 --fire --json-out bench/results/quake/multiplayer-browser-smoke-e1m7-remote-damage-visibility.json