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.

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

@@ -0,0 +1,18 @@
+pub mod build;
+pub mod config;
+pub mod files;
+pub mod format;
+pub mod git;
+pub mod lsp;
+pub mod outline;
+pub mod plugins;
+pub mod reason;
+pub mod references;
+pub mod run_state;
+pub mod search;
+pub mod settings;
+pub mod snippets;
+pub mod status;
+pub mod terminal;
+pub mod themes;
+pub mod type_graph;