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/relays/test/test_relays.c

@@ -1,10 +1,10 @@
 /* MC/DC harness for drivers/relays/relays.c.
  *
  * Two layers, one binary, so the combined run covers every decision in relays.c:
- *   1. unit tests through a FAKE relay_io — exercise the decision logic, incl.
+ *   1. unit tests through a FAKE relay_io: exercise the decision logic, incl.
  *      the export->node-appears path a passive tree cannot model.
  *   2. integration tests through the real sysfs backend + $WARDEN_GPIO_ROOT
- *      pointed at a scratch tree — exercise the backend's fopen/stat branches.
+ *      pointed at a scratch tree: exercise the backend's fopen/stat branches.
  */
 #include "../relays.h"