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/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "cortex-core"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+serde.workspace = true
+serde_json.workspace = true
+toml.workspace = true
+figment.workspace = true
+chrono.workspace = true
+anyhow.workspace = true
+thiserror.workspace = true
+tracing.workspace = true