[alexis900]

Fixes #466.

What

A raw keyboard event API for Ring 3, per the design doc docs/design/raw-keyboard-api-design.md.

• Kernel: input/kbd/ring.rs — KeyEvent (16-byte ABI), bounded lock-free SPSC KeyEventRing (overwrite oldest + dropped), and vk_from_scancode with the E0 split (KBD-EXTKEYS: Restaurar teclas extendidas (flechas/Home/End/Del) #391: E0 arrows no longer collide with the numpad). One ring + raw flag per VT (input/manager.rs); the ring is cleared when raw mode is enabled; raw is cleared when the foreground process exits.
• kbd::process_scancode emits every make/break with vk + modifiers and suppresses cooked byte delivery while raw.
• kwait::WaitReason::Keyboard { vt }; the keyboard IRQ wakes a blocked reader.
• ObInfoClass::KeyboardRead (44) / KeyboardPoll (45); ObSetInfoClass::KeyboardSetRawMode (55).
• libneodos: KeyEvent + VK_* table + kbd_set_raw / kbd_poll_event / kbd_read_event.
• userbin/keyread: enables raw, prints up to 10 make/break events, restores cooked.

VirtualBox evidence (NAT, e1000)

keyread in the guest:

  sc=30 vk=0 - down mod=32
  sc=30 vk=0 - up   mod=32
  sc=48 vk=0 - down mod=32
  sc=48 vk=0 - up   mod=32
  sc=42 vk=0 - down mod=33 ext
  sc=72 vk=38 UP down mod=33 ext
  sc=72 vk=38 UP up   mod=33 ext
  sc=42 vk=0 - up   mod=32 ext
  sc=29 vk=17 ? down mod=34
  sc=57 vk=32 SPACE down mod=34

a/b make/break, E0 Up arrow (vk=UP, ext), and Ctrl+Space (mod=34, vk=SPACE).

Tests

• QEMU neodev test: 960/960 (kbd_ring_push_pop_fifo, kbd_ring_overflow_drops_oldest, kbd_key_event_is_16_bytes, kbd_vk_extended_split).
• check-deps clean; check-irq-locks OK.

Deferred (documented)

sys_poll keyboard readiness and a distinct timeout status for the blocking read (the caller re-issues, like ob_wait). Raw codepoint is left 0 (clients use vk/scancode); text entry still goes through cooked stdin.

Note

Full packaging requires the one-line NeoDev image-allowlist addition (keyread), same as the other network/time userbins.