Fleet tools: add Rust version card (probe rustc + nightly latest + rustup update)

Adds Rust to the per-node dev-tool cards: daemon probes rustc → reports 'rust';
nightly checker fetches latest stable from GitHub rust-lang/rust; GET endpoint maps
rust→Rust (after docker); one-click update runs 'rustup update stable'. Frontend is
data-driven (no change). $HOME/.cargo/bin added to probe candidate dirs.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

crates/cm-api/src/routes/nodes.rs

@@ -199,6 +199,7 @@ pub async fn tools(
     // (probe key, display name, ui key) in display order; `glm` mirrors `claude`.
     let order = [
         ("docker", "Docker", "docker"),
+        ("rust", "Rust", "rust"),
         ("claude", "Claude Code", "claude"),
         ("kimi-cli", "Kimi", "kimi"),
         ("glm", "GLM (Claude Code)", "glm"),
@@ -230,7 +231,7 @@ pub async fn tool_update(
     nodes::get(&state.pool, node_id, user.workspace_id)
         .await?
         .ok_or(ApiError::NotFound)?;
-    if !["claude", "glm", "kimi", "ollama"].contains(&tool.as_str()) {
+    if !["claude", "glm", "kimi", "ollama", "rust"].contains(&tool.as_str()) {
         return Ok(Json(json!({ "ok": false, "output": "tool not updatable" })));
     }
     // ~180s: tool updates (npm/uv/brew/installer) legitimately run long.