feat: scaffold cortex workspace

Rust reverse-proxy for multi-node mistral.rs inference clusters.
Includes crate structure (cortex-core, cortex-gateway, cortex-agent,
cortex-cli), config loading, OpenAI/Anthropic translation stubs,
model routing, eviction, polling, and streaming proxy scaffolding.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/cortex-core/src/metrics.rs

@@ -0,0 +1,23 @@
+//! Request-level metrics captured by the gateway proxy layer.
+
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+
+/// Metrics captured for a single proxied request.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RequestMetrics {
+    pub timestamp: DateTime<Utc>,
+    pub model: String,
+    pub node: String,
+    pub prompt_tokens: u64,
+    pub completion_tokens: u64,
+    pub total_tokens: u64,
+    /// Tokens per second for the generation phase.
+    pub tok_per_sec: f64,
+    /// Time from request start to first SSE chunk (streaming) or full response.
+    pub time_to_first_token_ms: u64,
+    /// Total request latency including proxy overhead.
+    pub total_latency_ms: u64,
+    /// Whether this request triggered a model load (cold start).
+    pub cold_start: bool,
+}