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.

qemu/rs485-bridge/src/lib.rs

@@ -4,8 +4,8 @@
 //! what it believes is /dev/ttyS4); this bridge is the wire and every slave on
 //! it. Frames are delimited by an inter-frame gap of silence: RTU's 3.5-char
 //! rule cannot survive a socket transport, so a wall-clock gap stands in for it.
-//! A mis-split frame fails CRC inside `handle_frame`, which answers `None` —
-//! exactly a real slave staying silent — and the master already treats silence
+//! A mis-split frame fails CRC inside `handle_frame`, which answers `None`
+//! (exactly a real slave staying silent), and the master already treats silence
 //! as a timeout, so the failure mode degrades to a dropped poll, never a
 //! phantom reply.
 //!
@@ -26,7 +26,7 @@ pub const DEFAULT_GAP: Duration = Duration::from_millis(10);
 
 /// Accumulation cap: a Modbus RTU ADU is at most 256 bytes, so anything past
 /// 2x that without an inter-frame gap is a misbehaving master streaming
-/// continuously — drop the buffer instead of growing without bound.
+/// continuously. Drop the buffer instead of growing without bound.
 const MAX_PENDING: usize = 512;
 
 /// The shared bus: the slave plus its declared dimensions. The sim's register
@@ -75,11 +75,11 @@ pub fn pump_serial(
                 if buf.len() > MAX_PENDING {
                     // Rate-limit the log and back off for one gap so a master
                     // streaming continuously cannot peg a core and flood
-                    // stderr — mirroring the accept-loop backoff.
+                    // stderr, mirroring the accept-loop backoff.
                     discards += 1;
                     if discards == 1 || discards.is_multiple_of(256) {
                         eprintln!(
-                            "rs485: {} bytes buffered with no inter-frame gap — \
+                            "rs485: {} bytes buffered with no inter-frame gap, \
                              discarding (misbehaving master? {} discards so far)",
                             buf.len(),
                             discards
@@ -152,7 +152,7 @@ pub fn handle_control_line(line: &str, bus: &Bus) -> String {
         return format!("err trailing arguments after '{cmd}'");
     }
     // Each arm states its own bound (bus.regs for register space, bus.bits for
-    // bit space) INLINE — a previous string-keyed lookup defaulted silently to
+    // bit space) INLINE: a previous string-keyed lookup defaulted silently to
     // the bit bound, which would have handed a future `get-input` command the
     // wrong range and reintroduced the out-of-range panic this check prevents.
     let mut s = bus.slave.lock().unwrap();

qemu/rs485-bridge/src/main.rs

@@ -3,7 +3,7 @@
 //! control listener.
 //!
 //! Typical use (matches qemu/run.sh --rs485). Put the sockets in a private
-//! per-run directory (mktemp -d) — short (AF_UNIX caps paths at ~108 chars)
+//! per-run directory (mktemp -d): short (AF_UNIX caps paths at ~108 chars)
 //! and not guessable/pre-creatable by other local users, unlike a fixed
 //! /tmp name:
 //!
@@ -40,7 +40,7 @@ fn main() {
                 eprintln!("{name} needs a value");
                 usage()
             });
-            // A following flag means the value was omitted — report the real
+            // A following flag means the value was omitted. Report the real
             // problem instead of swallowing the flag as a bogus value.
             if v.starts_with("--") {
                 eprintln!("{name} needs a value, got flag '{v}'");
@@ -70,7 +70,7 @@ fn main() {
     if let Some(path) = control {
         // Clear a stale socket from a previous run. A failure here that is not
         // "nothing to remove" (e.g. someone else's file behind /tmp's sticky
-        // bit) will make the bind below fail — surface both errors.
+        // bit) will make the bind below fail. Surface both errors.
         let removed = std::fs::remove_file(&path);
         let listener = UnixListener::bind(&path).unwrap_or_else(|e| {
             eprintln!("FATAL: cannot bind control socket {path}: {e}");
@@ -89,7 +89,7 @@ fn main() {
                 let conn = match conn {
                     Ok(c) => c,
                     Err(e) => {
-                        eprintln!("rs485: control accept failed: {e} — backing off");
+                        eprintln!("rs485: control accept failed: {e}, backing off");
                         std::thread::sleep(Duration::from_millis(200));
                         continue;
                     }