Split crates/config/src/lib.rs (1441 lines) into engine/

Pure reorganization, no behavior change - verified by diffing the
function-name and struct/enum-name sets before/after (both identical)
plus a full cargo test pass. lib.rs is now a thin shim (mod
declarations + pub use) since a crate root can't itself become a
directory; all the actual content moved into engine/, split along the
Lua API's own srd.*/srd.window.*/srd.layout.*/srd.workspace.*/
srd.theme.* namespace groupings the file's own section comments
already used:

- mod.rs: SharedState, Engine, ConfigError, and Engine's core methods
  (new/get/set/dispatch/reload/...).
- register.rs: register_srd_module, which wires every fn_* builder
  from every other file into the srd Lua table - the one place that
  genuinely needs to see all of them.
- general.rs/window.rs/layout.rs/workspace.rs/theme.rs: the fn_*
  builder methods themselves, one file per srd.* sub-namespace.
- support.rs: free functions shared across those (do_reload,
  parse_direction, flatten_table_into, validate, default_config) and
  the WindowAction enum.
- tests.rs: the ~300-line test module, left unsplit for the same
  shared-helper reason manager/tests.rs and udev's tests were.

~40 fn_* methods and the support.rs free functions/enum went from
private to pub(super): called across what are now sibling submodules,
which Rust's privacy model doesn't let see each other's private items.

1 files changed, 42 insertions, 0 deletions

diff --git a/crates/config/src/engine/workspace.rs b/crates/config/src/engine/workspace.rs
new file mode 100644
index 0000000..a51e108
--- /dev/null
+++ b/crates/config/src/engine/workspace.rs
@@ -0,0 +1,42 @@
+use super::*;
+
+impl Engine {
+    // ---- srd.workspace.* ---------------------------------------------------
+
+    pub(super) fn fn_workspace_cycle(&self, forward: bool) -> Result<mlua::Function<'_>> {
+        let state = self.state.clone();
+        Ok(self.lua.create_function(move |_, ()| {
+            let wm = state.borrow().wm.clone();
+            let mut wm = wm.borrow_mut();
+            let ids: Vec<_> = wm.workspaces().iter().map(|w| w.id).collect();
+            if ids.is_empty() {
+                return Ok(());
+            }
+            let cur = wm.current_workspace();
+            let pos = ids.iter().position(|&id| id == cur).unwrap_or(0);
+            let next = if forward { (pos + 1) % ids.len() } else { (pos + ids.len() - 1) % ids.len() };
+            wm.switch_workspace(ids[next]);
+            Ok(())
+        })?)
+    }
+
+    pub(super) fn fn_workspace_switch(&self) -> Result<mlua::Function<'_>> {
+        let state = self.state.clone();
+        Ok(self.lua.create_function(move |_, id: usize| {
+            state.borrow().wm.borrow_mut().switch_workspace(id);
+            Ok(())
+        })?)
+    }
+
+    pub(super) fn fn_workspace_move_window(&self) -> Result<mlua::Function<'_>> {
+        let state = self.state.clone();
+        Ok(self.lua.create_function(move |_, id: usize| {
+            let wm = state.borrow().wm.clone();
+            let mut wm = wm.borrow_mut();
+            if let Some(focused) = wm.focused_id() {
+                wm.move_window_to_workspace(focused, id);
+            }
+            Ok(())
+        })?)
+    }
+}