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.

docs/decisions/0005-driver-source-of-truth.md

@@ -1,4 +1,4 @@
-# ADR 0005 — Driver Source of Truth
+# ADR 0005: Driver Source of Truth
 
 **Status:** Accepted (2026-08-25).
 
@@ -18,4 +18,4 @@ formalized as a patch series in `patches/`. flare-edge consumes this repo later
 - Realizes the seam architecture (ADR-referenced in `docs/architecture.md`).
 - flare-edge is not edited now; a later integration step points flare-edge at these.
 - Risk: temporary duplication of shared constants between the two repos until the
-  integration lands — tracked, acceptable for the bring-up window.
+  integration lands; tracked, acceptable for the bring-up window.