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/payload/README.md

@@ -1,7 +1,7 @@
 # Guest Payloads
 
 Drop **static musl armv7** binaries in this directory (contents are
-gitignored — binaries are never committed); `qemu/mkimage.sh` copies everything
+gitignored; binaries are never committed); `qemu/mkimage.sh` copies everything
 in this directory (except this README) into `/usr/bin/` of both rootfs slots.
 Static musl is the same target the device uses for its Rust daemons, so the
 exact production binaries run unmodified in the VM.
@@ -21,6 +21,6 @@ cp <flare-edge>/target/armv7-unknown-linux-musleabihf/release/warden-flared qemu
 ```
 
 Stage-2 init starts `warden-flared`, `warden-modbus`, and `warden-ui` (the
-UI additionally needs `--display on|headless` + the virt.fragment kernel for
+UI also needs `--display on|headless` + the virt.fragment kernel for
 /dev/fb0) automatically when present (logs land in `/tmp/<name>.log` inside
-the guest). An empty payload is valid — the image boots busybox-only.
+the guest). An empty payload is valid: the image boots busybox-only.