10230 Deepseek Native Max Effort - Omniroute

fix(api): DeepSeek V4's native max reasoning tier is now reachable. DeepSeek accepts reasoning_effort low/high/max and maps medium/xhigh down to high, while OmniRoute's canonical vocabulary collapses max onto xhigh — so {"effort":"max"} silently resolved to high and the catalog never advertised a max tier (or its <model>-max variant). Following the existing extendCodexGpt56EffortValues precedent, the native tier is now preserved for deepseek/ds V4 models only; the global effort vocabulary is unchanged, routed namespaces (openrouter/deepseek/…, tllm/deepseek_v4, oc/deepseek-v4-flash-free) keep the canonical behavior, and an explicit client reasoning_effort still wins (#10230) — thanks @Neuron-Mr-White