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/mkinitramfs.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 # Build the QEMU device-sim initramfs: the pinned static busybox + qemu/rootfs/.
-# The busybox binary is the ONLY external input (sha256-pinned, fail-closed —
+# The busybox binary is the ONLY external input (sha256-pinned, fail-closed:
 # see qemu/lib.sh).
 #
 # Env: