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.

kernel/rv1106-enablement/build-m2.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# build-m2.sh — reproducible M2 (earlycon) build of the RV1106 → 6.18 forward-port.
+# build-m2.sh: reproducible M2 (earlycon) build of the RV1106 -> 6.18 forward-port.
 #
 # Produces: a zImage with our ported SoC drivers, and rv1106-warden-m2.dtb.
 # Boot is a separate on-hardware step (see PORT-STATUS.md "M2 boot").