fix: capacities single-sourced in types (display MAX_WINDOWS/BUFFER_PAGES, storage MAX_CLIENTS), display + storage budgets derived from them, const asserts on VA layouts; kernel regions 64 -> 256

crates/types/src/display.rs

@@ -139,6 +139,12 @@ pub mod window {
     pub const BADGE: usize = 1 << 61;
     pub const OK: usize = 0;
     pub const PIXEL_BYTES: usize = 4;
+    /// Windows open at once. Each has a pixel buffer of the display's (as
+    /// does the screen), so this is what the display's budget is made of.
+    pub const MAX_WINDOWS: usize = 8;
+    /// The most a pixel buffer (a window's, the screen's) takes: room for
+    /// 1280x800.
+    pub const BUFFER_PAGES: usize = 1024;
     /// Longest name the OS bar shows.
     pub use crate::name::BYTES as NAME_BYTES;
 

crates/types/src/storage.rs

@@ -4,6 +4,10 @@
 
 /// Size of each client's buffer.
 pub const BUFFER_PAGES: usize = 16;
+/// Connections at once (every program reading files, apps among them):
+/// each has a buffer of storage's, so this is what storage's budget is
+/// made of.
+pub const MAX_CLIENTS: usize = 16;
 pub const BUFFER_SIZE: usize = BUFFER_PAGES * 4096;
 /// Longest path the server will look at.
 pub const MAX_PATH: usize = 255;