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.

sim/benches/sim_bench.rs

@@ -3,7 +3,7 @@
 //! Dependency-free (`harness = false`): a fixed-iteration timing loop, so the sim
 //! crate keeps zero deps and CI can capture a stable ns/op number per model with no
 //! criterion tree to compile. Human-readable timings go to stdout; one JSON line per
-//! benchmark goes to stderr for CI trend capture (`bench: … ns_per_op …`).
+//! benchmark goes to stderr for CI trend capture (`bench: ... ns_per_op ...`).
 //!
 //! Run: `cargo bench` (or `cargo run --release --bench sim_bench`).