docs: full docs-vs-code audit — fix every stale claim across 40 docs

Every doc verified claim-by-claim against the code by parallel audit agents,
then fixed and adversarially re-verified. Two waves of staleness corrected:
the originally audited findings (higher-half boot handoff, kernel VFS
takeover, fault isolation + claim release + driver restart, AML/S5 moving to
ring 3, threading's shipped design, USB+FAT landing) and a second pass of
adjacent claims the verifiers caught (smp.md 'not built yet' intro,
system-requirements' PS/2-only and no-storage claims, halting.md's red-panic
and no-IDT text, testing.md's serial mirroring, router-era vfs-protocol
wording, capsule-first boot loading).

threading.md now documents the shared-fate gap explicitly: the design says a
process dies whole, the kernel today kills only the offending thread.

Also fixes three stale code comments (isr.s exceptionHandler, acpi.zig
sleepValue, build.zig boot-volume) — comments only, no behavior change.

docs/logging.md

@@ -5,8 +5,11 @@ and every service must run correctly with zero output channels. On top of that
 rule, danos has **per-process logging** — every process's output is attributed
 by the kernel and lands in its own file on the flash volume, which is what makes
 a headless real machine (no serial port) debuggable. The display (the
-framebuffer surface) is a separate concern and deliberately not a log sink;
-`main.zig` mirrors a few user-facing status lines and panics to it explicitly.
+framebuffer surface) is a separate concern with one bootstrap exception: the
+kernel's framebuffer console (`system/kernel/console.zig`) joins the log sinks
+at boot, so the whole transcript shows on screen until the display service
+claims the framebuffer and silences it; after that only panic/fatal messages
+are mirrored to it explicitly (`system/kernel/kernel.zig`).
 
 ## The pipeline
 
@@ -37,7 +40,8 @@ kernel log.print ─┘                            │
    8-byte aligned.
 
 4. **Render.** Registered sinks (serial under `-Dserial`, the 0xE9 debug
-   console) get a live transcript: kernel/raw output verbatim, leveled records
+   console, and the framebuffer console until the display service claims the
+   screen) get a live transcript: kernel/raw output verbatim, leveled records
    as `<binary path>: message` — one composed write per line, under the log's
    own spinlock (never the big kernel lock; panic paths try-acquire with a
    bound and fall back to sinks-only). Sinks are best-effort and self-guarding;