Split crates/core/src/manager.rs (2048 lines) into manager/

Pure reorganization, no behavior change - verified by diffing the
function-name set before/after (identical 130 functions) plus a full
cargo test pass. WindowManager's struct/field definitions, Default,
new(), and the three trivial constructors (add_rule/register_layout/
available_layouts) stay in mod.rs; the rest of the single ~950-line
impl block is split into one file per the section comments the file
already had (monitors, windows, focus, winops, hittest, dragresize,
workspaces, layout). Three methods called across section boundaries
(monitor_for, windows_on_workspace, cycle_focus) went from private to
pub(super) - Rust's privacy model doesn't let sibling submodules see
each other's private items, only a defining module's own descendants.

The ~1000-line test module moves to manager/tests.rs unsplit: its
helpers (wm_with_monitor, two_monitors, monitor_with_dock) are shared
across tests for every section, so splitting further would mean
duplicating them or adding another shared-support file for little
benefit.

0 files changed, 0 insertions, 0 deletions