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/blkdevparts.conf

@@ -1,10 +1,10 @@
 # The device's canonical 12-partition A/B layout, expressed for the VM's
 # virtio disk (vda). On hardware the same string names mmcblk0 and is baked
-# into the U-Boot env — source: flare-edge docs/decisions/0003-partition-layout.md.
+# into the U-Boot env; source: flare-edge docs/decisions/0003-partition-layout.md.
 # There is no MBR/GPT anywhere: U-Boot and Linux both parse this string, which
 # is why handing it to the VM kernel on the cmdline reproduces the exact
 # partition map (vda9 = rootfs_a = hardware mmcblk0p9).
 #
 # Sourced by qemu/mkimage.sh (computes byte offsets from it) and qemu/run.sh
-# (passes it verbatim in -append). Single source of truth — edit only here.
+# (passes it verbatim in -append). Single source of truth: edit only here.
 WARDEN_BLKDEVPARTS='vda:32K(env),512K@32K(idblock),512K(uboot),512K(misc),32M(boot_a),32M(boot_b),128M(oem_a),128M(oem_b),1G(rootfs_a),1G(rootfs_b),32M(recovery),1G(userdata)'