Built device interrupts

docs/README.md

@@ -25,7 +25,10 @@ rather than restate it. Roughly in the order things happen at runtime:
 7. **[paging.md](paging.md) — the kernel's page tables.** Building our own 4-level
    page tables, identity-mapping the low 4 GiB, and switching CR3 off the firmware's
    tables onto ours.
-8. **[halting.md](halting.md) — halting.** Why a kernel can't just "exit", and
+8. **[device-interrupts.md](device-interrupts.md) — device interrupts.** The Local
+   APIC and its timer — the kernel's first interrupt that is *handled and returned
+   from*, giving it a heartbeat.
+9. **[halting.md](halting.md) — halting.** Why a kernel can't just "exit", and
    how `while (true) hlt` parks the CPU safely once there's nothing left to do.
 
 Cutting across all of these:
@@ -46,6 +49,7 @@ map** of physical RAM ([memory-map.md](memory-map.md)); the kernel turns that ma
 into a **frame allocator** ([frame-allocator.md](frame-allocator.md)), installs
 its **descriptor tables** so CPU faults are caught ([interrupts.md](interrupts.md)),
 builds its own **page tables** and switches onto them ([paging.md](paging.md)),
+starts the **timer** so it has a heartbeat ([device-interrupts.md](device-interrupts.md)),
 runs — its CPU-specific bits behind the [arch](arch.md) boundary — and when it has
 finished, or panics, it **halts** ([halting.md](halting.md)).
 
@@ -59,6 +63,6 @@ finished, or panics, it **halts** ([halting.md](halting.md)).
 | Physical frame allocator | `src/pmm.zig` |
 | Framebuffer text console (mirrors to serial) | `src/console.zig` |
 | In-kernel test cases | `src/tests.zig` |
-| Arch-specific kernel code (`halt`, GDT/IDT/TSS, exception stubs, page tables, serial, linker script) | `src/arch/x86_64/` |
+| Arch-specific kernel code (`halt`, GDT/IDT/TSS, exception + interrupt stubs, page tables, APIC/timer, serial, linker script) | `src/arch/x86_64/` |
 | Build + `run-efi` (QEMU/OVMF) | `build.zig` |
 | QEMU integration test harness | `test/qemu_test.py` |