wm: integrate home terminal as window 0 + fix console focus after close

- wm rewrite: chrome flag per window, create_home_window for the
  console (window 0, chrome-less, bottom-pinned, never closed),
  composite_rect fills desktop background then blits windows bottom-to-top,
  draw_window_intersect handles chrome-less windows, hit_test returns
  Content for chrome-less, destroy/move_window no-op for id 0.

- vt: add window_params() so main.rs can wire the Terminal to wm window 0.

- main.rs: create home terminal window 0 and attach Terminal after wm::init().

- Focus fix: focus(0) now stores CONSOLE sentinel (not raw 0) so
  focused() returns None when the home terminal has focus. Without this,
  closing a GUI window left FOCUSED=0, which tty::poll_key() interpreted
  as 'a GUI app has focus', spinning forever and swallowing all keyboard
  input.

1 files changed, 14 insertions, 1 deletions

diff --git a/rsnix/src/vt.rs b/rsnix/src/vt.rs
index 90264f6..12e2cdc 100644
--- a/rsnix/src/vt.rs
+++ b/rsnix/src/vt.rs
@@ -80,6 +80,7 @@ pub struct Terminal {
     cur: usize,
     pending_scrolls: usize,
     last_sync_tick: u64,
+    dirty_all: bool,
     buffer: Vec<u32>,
     w: usize,
     h: usize,
@@ -128,6 +129,7 @@ impl Terminal {
             cur: 0,
             pending_scrolls: 0,
             last_sync_tick: 0,
+            dirty_all: true,
             buffer: vec![0; w * h],
             w,
             h,
@@ -140,6 +142,11 @@ impl Terminal {
         self.window_id = Some(id);
     }
 
+    /// Buffer pointer and pixel dimensions (for the WM to composite).
+    pub fn window_params(&self) -> (*const u32, usize, usize) {
+        (self.buffer.as_ptr(), self.w, self.h)
+    }
+
     pub fn ready(&self) -> bool {
         self.rows != 0
     }
@@ -193,6 +200,7 @@ impl Terminal {
         }
         self.pending_scrolls = 0;
         self.last_sync_tick = crate::interrupts::TICKS.load(core::sync::atomic::Ordering::Relaxed);
+        self.dirty_all = true;
         self.flush();
     }
 
@@ -509,7 +517,12 @@ impl Terminal {
         let n = rows * cols;
         let cursor_visible = self.cursor_visible;
         let (cr, cc) = (self.cursor_r, self.cursor_c);
-        let mut dirty: Option<(usize, usize, usize, usize)> = None;
+        let mut dirty = if self.dirty_all {
+            self.dirty_all = false;
+            Some((0, 0, self.w, self.h))
+        } else {
+            None
+        };
 
         // Diff cells vs rendered, re-blitting changed cells into the buffer.
         for i in 0..n {