docs: ASCII typography and style normalization across all repo text

Replace every em dash with real punctuation (rewrites, not hyphen swaps)
in docs, code comments, scripts, configs, and the port records; convert
en dashes, curly quotes, ellipsis glyphs, arrows, and section signs to
ASCII; drop machine-writing tell phrases from living docs. ADR titles
now use a colon. The M2 bring-up DTS model string carried an em dash
into the patch series and its record echoes; fixed at both, and the full
series re-verified to apply cleanly onto pristine 6.18.46. One comment
in freshness.h deliberately names the em dash glyph the UI renders as
the unknown mark; that is data, kept as prose naming it.

Verified: cargo tests (sim, config-lint, rs485-bridge), shellcheck,
both driver MC/DC harnesses, patches-apply.

qemu/tests/boot-smoke.sh

@@ -11,16 +11,16 @@ QDIR="$(cd "$HERE/.." && pwd)"                           # qemu/
 
 ZIMAGE="${1:-}"
 if [ -z "$ZIMAGE" ] || [ ! -f "$ZIMAGE" ]; then
-  echo "FATAL: usage: $0 <zImage> [initramfs] — zImage missing or not a file: '${ZIMAGE:-}'" >&2
+  echo "FATAL: usage: $0 <zImage> [initramfs]: zImage missing or not a file: '${ZIMAGE:-}'" >&2
   exit 1
 fi
 INITRD="${2:-$QDIR/out/initramfs.cpio.gz}"
 [ -f "$INITRD" ] || {
-  echo "FATAL: initramfs not found at $INITRD — run qemu/mkinitramfs.sh first" >&2
+  echo "FATAL: initramfs not found at $INITRD: run qemu/mkinitramfs.sh first" >&2
   exit 1
 }
 command -v qemu-system-arm >/dev/null || {
-  echo "FATAL: qemu-system-arm not on PATH (apt-get install qemu-system-arm) — see qemu/README.md" >&2
+  echo "FATAL: qemu-system-arm not on PATH (apt-get install qemu-system-arm): see qemu/README.md" >&2
   exit 1
 }
 
@@ -29,7 +29,7 @@ trap 'rm -f "$LOG"' EXIT
 
 # Delegate the qemu invocation to run.sh (--no-disk) so the machine shape
 # (-M virt,highmem=off, cpu, memory, virtio topology) lives in exactly one
-# place — the two hand-copied invocations had already drifted once.
+# place: the two hand-copied invocations had already drifted once.
 # timeout -k: a wedged qemu that ignores SIGTERM gets SIGKILLed 10s later
 # instead of holding the job until the workflow-level timeout.
 timeout -k 10 180 bash "$QDIR/run.sh" \