shell: ^C cancels the line / aborts streams, ^D = EOF → poweroff

- ps2: Ctrl+C and Ctrl+D are now KeyEvents (ctrl modifier + c/d map);
  other Ctrl+key combos are swallowed
- shell read_line: ^C clears the line and echoes '^C' (bash-style),
  ^D on an empty line echoes '^D' and shuts down (EOF), ^D with text
  on the line is ignored
- cat/hexdump stream incrementally (was: build whole string then print)
  and check for ^C between chunks, so a running dump can be aborted
- verified in QEMU: line cancel, standalone interrupt, ^C aborts an
  infinite 'cat /dev/zero' stream, ^D powers off

1 files changed, 11 insertions, 0 deletions

diff --git a/rsnix/src/ps2.rs b/rsnix/src/ps2.rs
index 477d146..1b10b3b 100644
--- a/rsnix/src/ps2.rs
+++ b/rsnix/src/ps2.rs
@@ -22,6 +22,8 @@ pub enum KeyEvent {
     Backspace,
     Tab,
     Escape,
+    CtrlC,
+    CtrlD,
     ArrowUp,
     ArrowDown,
     ArrowLeft,
@@ -304,6 +306,15 @@ fn process_byte(byte: u8) -> Option<KeyEvent> {
                     ch.to_ascii_uppercase()
                 };
             }
+            // Ctrl+letter — the shell uses ^C (interrupt) and ^D (EOF).
+            let ctrl = state.modifiers & (MOD_LCTRL | MOD_RCTRL) != 0;
+            if ctrl {
+                return match ch.to_ascii_lowercase() {
+                    b'c' => Some(KeyEvent::CtrlC),
+                    b'd' => Some(KeyEvent::CtrlD),
+                    _ => None, // swallow other Ctrl+key combinations
+                };
+            }
             if ch != 0 {
                 Some(KeyEvent::Char(ch as char))
             } else {