Windowed GUI: wm module, input routing, and the paint app

- Add the wm window-manager facility per ADR 0004: overlapping
  pixel-surface windows, damage-rectangle compositing, WM-drawn title
  bar, focus/minimize/close, and F1-F4 keybindings
- Add gop shadow compositing primitives and vt::repaint_region so the
  console stays layer 0 beneath windows
- Route mouse (absolute coords, press/release edges) and keyboard
  (focus-aware input pump) to the focused window
- Add the rspaint drawing-program crate (pen, 8 colors, clear) and shell
  draw/windows/restore commands
- Extend TaskMsg with AppMouse/Focus/Close and document the design in
  CONTEXT.md + ADR 0004

1 files changed, 37 insertions, 22 deletions

diff --git a/rsnix/src/sched.rs b/rsnix/src/sched.rs
index 259ddf6..39ecb65 100644
--- a/rsnix/src/sched.rs
+++ b/rsnix/src/sched.rs
@@ -59,6 +59,9 @@ const MSG_CAP: usize = 16;
 pub enum TaskMsg {
     Key(crate::ps2::KeyEvent),
     Mouse(crate::ps2::MouseEvent),
+    AppMouse(crate::ps2::AppMouseEvent),
+    Focus(bool),
+    Close,
     Timer,
     User(u64),
 }
@@ -94,6 +97,11 @@ pub fn msg_describe(msg: &TaskMsg) -> alloc::string::String {
             if m.left { "L" } else { "-" },
             if m.right { "R" } else { "-" }
         ),
+        TaskMsg::AppMouse(m) => {
+            alloc::format!("AppMouse({},{} {:?} b={:#x})", m.x, m.y, m.kind, m.buttons)
+        }
+        TaskMsg::Focus(f) => alloc::format!("Focus({})", f),
+        TaskMsg::Close => "Close".into(),
         TaskMsg::Timer => "Timer".into(),
         TaskMsg::User(n) => alloc::format!("User({})", n),
     }
@@ -179,7 +187,10 @@ struct SpinWatch {
     last_rsp: usize,
     same: u32,
 }
-const SPIN_WATCH_INIT: SpinWatch = SpinWatch { last_rsp: 0, same: 0 };
+const SPIN_WATCH_INIT: SpinWatch = SpinWatch {
+    last_rsp: 0,
+    same: 0,
+};
 static mut SPIN_WATCH: [SpinWatch; MAX_TASKS] = [SPIN_WATCH_INIT; MAX_TASKS];
 /// A spinning background task is interrupted at roughly half the tick rate
 /// (it alternates with idle), so 1500 hits is ~30 s of wall time.
@@ -381,11 +392,7 @@ pub fn spawn(entry: fn(), name: &str) -> Option<usize> {
     };
     let ok = spawn_at(id, entry, name);
     unlock();
-    if ok {
-        Some(id)
-    } else {
-        None
-    }
+    if ok { Some(id) } else { None }
 }
 
 unsafe fn reap(id: usize) {
@@ -698,10 +705,12 @@ pub(crate) fn fault_dump(kind: &str, cr2: u64, frame: &crate::interrupts::IntFra
             }
             let ra = *(fp as *const u64).add(1); // [rbp+8] = return address
             if let Some((start, end)) = filter
-                && ra >= start as u64 && ra < end as u64 {
-                    bt[bn] = ra;
-                    bn += 1;
-                }
+                && ra >= start as u64
+                && ra < end as u64
+            {
+                bt[bn] = ra;
+                bn += 1;
+            }
             let nfp = *(fp as *const u64);
             if nfp <= fp {
                 break; // chain must grow upward
@@ -715,19 +724,21 @@ pub(crate) fn fault_dump(kind: &str, cr2: u64, frame: &crate::interrupts::IntFra
         while p + 8 <= limit && bn < bt.len() {
             let v = *(p as *const u64);
             if let Some((start, end)) = filter
-                && v >= start as u64 && v < end as u64 {
-                    let mut dup = false;
-                    for i in 0..bn {
-                        if bt[i] == v {
-                            dup = true;
-                            break;
-                        }
-                    }
-                    if !dup {
-                        bt[bn] = v;
-                        bn += 1;
+                && v >= start as u64
+                && v < end as u64
+            {
+                let mut dup = false;
+                for i in 0..bn {
+                    if bt[i] == v {
+                        dup = true;
+                        break;
                     }
                 }
+                if !dup {
+                    bt[bn] = v;
+                    bn += 1;
+                }
+            }
             p += 8;
         }
     }
@@ -842,7 +853,11 @@ pub(crate) fn fault_dump(kind: &str, cr2: u64, frame: &crate::interrupts::IntFra
             &mut w,
             core::format_args!(
                 "rax={:#x} rcx={:#x} rdx={:#x} rsi={:#x} rdi={:#x}",
-                frame.rax, frame.rcx, frame.rdx, frame.rsi, frame.rdi
+                frame.rax,
+                frame.rcx,
+                frame.rdx,
+                frame.rsi,
+                frame.rdi
             ),
         );
         w.len()