pvKernel 0.0.4 — Hardware Interrupts and Timer

[ultronstudio]

pvKernel 0.0.4 is out: https://github.com/ultronstudio/pvkernel/releases/tag/v0.0.4

This release lets pvKernel safely receive hardware interrupts for the first time:

• A legacy dual 8259 PIC driver, remapped to IRQ vectors 32-47, with per-line
  masking/unmasking, correct EOI/cascade handling, and spurious IRQ7/IRQ15
  detection.
• A PIT channel 0 periodic timer (~100 Hz) with an atomic tick counter.
• IDT handlers for all 16 remapped IRQ vectors, so no interrupt line is ever
  left unhandled.
• A boot-time verification that maskable interrupts can be safely enabled and
  that timer ticks are repeatedly delivered, followed by an interrupt-enabled
  idle loop instead of an immediate halt.
• Deterministic headless QEMU tests (isa-debug-exit), now running in CI on
  every pull request and push to main.

See CHANGELOG.md
for details, and the new
docs/architecture/hardware-interrupts.md,
docs/architecture/timer.md,
and docs/development/testing.md
for the design rationale and how to run the tests locally.

Out of scope for this milestone: APIC, keyboard input, any IRQ line other than
the timer, memory allocation, and scheduling — see
ROADMAP.md for
what's next.