rename crates/ → vessels/ — El's word for buildable units

Per the consolidation onto El: 'crates' is the Rust word, 'vessel' is
El's (per spec/language.md §15). The directory rename is the structural
marker that this slot holds an El buildable unit, even if its current
contents are still Rust pending port.

Mechanical: git mv crates vessels, sed workspace members and any path
dependencies, update CI workflow paths, update README references.
Cross-repo path dependencies (`../foo/crates/bar`) updated workspace-
wide so cargo metadata still resolves where the Rust still builds.

ide/vessels/el-ide-server/src/api/run_state.rs

@@ -0,0 +1,19 @@
+//! Run state — tracks the currently running process so it can be killed.
+
+use std::sync::Arc;
+use tokio::sync::Mutex;
+use tokio::process::Child;
+
+/// Global run state shared across request handlers.
+#[derive(Default)]
+pub struct RunState {
+    pub current_child: Mutex<Option<Child>>,
+}
+
+impl RunState {
+    pub fn new() -> Arc<Self> {
+        Arc::new(Self {
+            current_child: Mutex::new(None),
+        })
+    }
+}