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.

drivers/freshness/test/Makefile

@@ -1,7 +1,7 @@
 # MC/DC unit harness for drivers/freshness/freshness.c (the UI stale-number guard).
 #
-#   make check   — build, run, FAIL unless freshness.c hits 100% MC/DC + all checks.
-#   make report  — per-condition gcov annotation.
+#   make check   : build, run, FAIL unless freshness.c hits 100% MC/DC + all checks.
+#   make report  : per-condition gcov annotation.
 #   make clean
 #
 # FRESH_MAX is forced to 2 so the "binding table full -> NULL" path is reachable