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/rootfs/etc/warden-lib.sh

@@ -1,11 +1,11 @@
 # shellcheck shell=sh
 # Shared helpers for the VM's stage-1 (/init + /etc/rc, initramfs) and stage-2
 # (/sbin/init, disk rootfs) boot scripts. Present in both filesystems because
-# both are staged from the same qemu/rootfs/ skeleton. ONE copy of each rule —
+# both are staged from the same qemu/rootfs/ skeleton. ONE copy of each rule:
 # the slot-validation drift between two hand-copied parsers was a real
 # review finding.
 
-# Populate /dev/block/by-name/<PARTNAME> symlinks from sysfs uevents — the
+# Populate /dev/block/by-name/<PARTNAME> symlinks from sysfs uevents: the
 # contract flare-edge's slotctl.rs relies on. blkdevparts= gives every vda
 # partition a PARTNAME.
 warden_populate_by_name() {
@@ -26,7 +26,7 @@ warden_populate_by_name() {
 }
 
 # Parse warden.slot= from the cmdline (whole-token, never substring) and
-# VALIDATE it — echoes "_a" or "_b", falling back to _a with a warning.
+# VALIDATE it: echoes "_a" or "_b", falling back to _a with a warning.
 warden_slot() {
     slot="_a"
     # shellcheck disable=SC2013 # cmdline TOKENS are the unit here, not lines