Add per-window resize-margin override (Hyprland's extend_border_grab_area)

MISSING.md had listed this as needing to touch srdwm_core::window::
hit_test's signature at every call site, including the honest-stub
Windows/macOS backends - overstated on closer inspection: that shared
function already takes a plain resize_margin: i32 parameter, agnostic
to where the value comes from. The only real change needed was reading
Window.resize_margin.unwrap_or(wm-wide default) instead of always the
WM-wide value, at the single call site inside WindowManager::hit_test
in core - no backend touched at all.

Window.resize_margin: Option<i32>, WindowRuleActions.resize_margin to
match, applied in add_window/reapply_rules_if_pending the same way
opacity already is. Settable via a rule action or
srd.window.set_resize_margin(n) on the focused window.

1 files changed, 17 insertions, 0 deletions

diff --git a/crates/core/src/manager/tests.rs b/crates/core/src/manager/tests.rs
index 24e8932..e1518f1 100644
--- a/crates/core/src/manager/tests.rs
+++ b/crates/core/src/manager/tests.rs
@@ -246,6 +246,23 @@
     }
 
     #[test]
+    fn per_window_resize_margin_overrides_the_wm_wide_default() {
+        // Hyprland's per-window `extend_border_grab_area` equivalent.
+        let mut wm = wm_with_monitor();
+        wm.set_layout(wm.current_workspace(), "tiling"); // keeps add_window from overriding geometry via SmartPlacement
+        let id = wm.alloc_window_id();
+        let mut w = Window::new(id, "a");
+        w.geometry = Rect::new(100, 100, 400, 300);
+        w.resize_margin = Some(30);
+        wm.add_window(w);
+
+        // 15px in from the left edge: well past the WM-wide default (6px),
+        // but still inside this window's own wider 30px override.
+        let hit = wm.hit_test(115, 250);
+        assert_eq!(hit.map(|(_, h)| h), Some(TitlebarHit::Resize(ResizeEdge::Left)));
+    }
+
+    #[test]
     fn moving_window_to_another_workspace_removes_it_from_current() {
         let mut wm = wm_with_monitor();
         let a = wm.alloc_window_id();