refactor: cortex talks to neurons instead of mistral.rs directly

Replace NodeConfig (static vram_mb, pinned) with NeuronEndpoint.
Hardware discovery and model pinning now come from neuron API and
models.toml catalogue respectively.

- config.rs: nodes -> neurons, add models_config path
- catalogue.rs: ModelProfile with pinned_on, ModelCatalogue
- poller.rs: poll neuron GET /models (ModelInfo format)
- router.rs: resolve inference endpoint via neuron GET /models/{id}/endpoint
- evictor.rs: call neuron POST /models/unload
- node.rs: remove vram_mb, pinned fields (come from discovery/catalogue)
- All 22 gateway tests updated to mock neuron API
- Remove MistralModelsResponse, ModelLifecycleRequest (no longer needed)

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

crates/cortex-gateway/src/poller.rs

@@ -1,15 +1,16 @@
-//! Background poller that periodically queries each node's `/v1/models`
-//! endpoint to refresh the fleet state.
+//! Background poller that periodically queries each neuron's API
+//! to refresh the fleet state.
 
 use crate::state::CortexState;
 use chrono::Utc;
-use cortex_core::node::{MistralModelsResponse, ModelEntry, ModelStatus};
+use cortex_core::harness::ModelInfo;
+use cortex_core::node::{ModelEntry, ModelStatus};
 use std::sync::Arc;
 use std::time::Duration;
 
 const POLL_INTERVAL: Duration = Duration::from_secs(10);
 
-/// Runs forever, polling all nodes on a fixed interval.
+/// Runs forever, polling all neurons on a fixed interval.
 pub async fn poll_loop(fleet: Arc<CortexState>) {
     loop {
         poll_once(&fleet).await;
@@ -17,15 +18,15 @@ pub async fn poll_loop(fleet: Arc<CortexState>) {
     }
 }
 
-/// Poll all nodes once. Used by `poll_loop` and available for testing.
+/// Poll all neurons once. Used by `poll_loop` and available for testing.
 pub async fn poll_once(fleet: &CortexState) {
-    for nc in &fleet.node_configs {
-        poll_node(fleet, &nc.name, &nc.endpoint).await;
+    for nc in &fleet.neuron_configs {
+        poll_neuron(fleet, &nc.name, &nc.endpoint).await;
     }
 }
 
-async fn poll_node(fleet: &CortexState, name: &str, endpoint: &str) {
-    let url = format!("{endpoint}/v1/models");
+async fn poll_neuron(fleet: &CortexState, name: &str, endpoint: &str) {
+    let url = format!("{endpoint}/models");
 
     let result = fleet
         .http_client
@@ -41,38 +42,36 @@ async fn poll_node(fleet: &CortexState, name: &str, endpoint: &str) {
 
     match result {
         Ok(resp) if resp.status().is_success() => {
-            match resp.json::<MistralModelsResponse>().await {
-                Ok(models_resp) => {
-                    // Merge upstream model list into our state, preserving
-                    // our local metadata (last_accessed, vram_estimate).
+            match resp.json::<Vec<ModelInfo>>().await {
+                Ok(models) => {
                     let mut seen = std::collections::HashSet::new();
-                    for upstream in &models_resp.data {
+                    for upstream in &models {
                         seen.insert(upstream.id.clone());
-                        let status = parse_status(upstream.status.as_deref());
+                        let status = parse_status(&upstream.status);
 
                         node.models
                             .entry(upstream.id.clone())
                             .and_modify(|e| {
                                 e.status = status;
+                                e.vram_estimate_mb = upstream.vram_used_mb;
                             })
                             .or_insert_with(|| ModelEntry {
                                 id: upstream.id.clone(),
                                 status,
                                 last_accessed: None,
-                                vram_estimate_mb: None,
+                                vram_estimate_mb: upstream.vram_used_mb,
                             });
                     }
 
-                    // Remove models that are no longer reported by the node
-                    // (e.g. after a config change / restart).
+                    // Remove models no longer reported by the neuron.
                     node.models.retain(|id, _| seen.contains(id));
 
                     node.healthy = true;
                     node.last_poll = Some(Utc::now());
-                    tracing::debug!(node = name, models = models_resp.data.len(), "poll ok");
+                    tracing::debug!(node = name, models = models.len(), "poll ok");
                 }
                 Err(e) => {
-                    tracing::warn!(node = name, error = %e, "failed to parse /v1/models response");
+                    tracing::warn!(node = name, error = %e, "failed to parse /models response");
                     node.healthy = false;
                 }
             }
@@ -81,24 +80,22 @@ async fn poll_node(fleet: &CortexState, name: &str, endpoint: &str) {
             tracing::warn!(
                 node = name,
                 status = %resp.status(),
-                "node returned non-success status"
+                "neuron returned non-success status"
             );
             node.healthy = false;
         }
         Err(e) => {
-            tracing::warn!(node = name, error = %e, "failed to reach node");
+            tracing::warn!(node = name, error = %e, "failed to reach neuron");
             node.healthy = false;
         }
     }
 }
 
-fn parse_status(s: Option<&str>) -> ModelStatus {
+fn parse_status(s: &str) -> ModelStatus {
     match s {
-        Some("loaded") => ModelStatus::Loaded,
-        Some("unloaded") => ModelStatus::Unloaded,
-        Some("reloading") => ModelStatus::Reloading,
-        // If the status field is absent, assume loaded (older mistral.rs versions
-        // may not include it).
+        "loaded" => ModelStatus::Loaded,
+        "unloaded" => ModelStatus::Unloaded,
+        "reloading" => ModelStatus::Reloading,
         _ => ModelStatus::Loaded,
     }
 }