Remove machine-writing tells from comments and docs

Emoji markers, markdown bold inside code comments, and em-dashes are
gone from source comments, string literals, scripts, Gradle files and
the markdown docs. Counted before and after:

  emoji markers   2680 -> 1 (the emoji picker's own list, which is the feature)
  em-dashes       2490 -> 9 (table placeholders and fenced code)

Two warning glyphs in user-facing strings in ChatScreens.kt are removed
as well; the sentences say the same thing without them. Two backtick
test names carried an em-dash and now carry a comma.

Nothing else changed. 1208 tests pass, counted from the result XML.
The three obfs4 interop tests are opted out with OBFS4_INTEROP_OPTOUT=1
for this run, as their own message instructs when no bridge is set up.

CONTRIBUTING gets a four-line rule so it does not grow back.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

scripts/release-manifest.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # Write the update manifest for a built APK.
 #
-# 🔴 The version in the manifest is read back OUT of the APK, never typed. A
+# The version in the manifest is read back OUT of the APK, never typed. A
 # manifest that claims a version the APK is not is worse than no manifest: it
 # either offers an update that installs as the same build (and so appears to do
 # nothing), or fails to offer one that exists. Reading it from the artifact is
@@ -27,23 +27,23 @@ name="$(sed -n "s/.*versionName='\([^']*\)'.*/\1/p" <<<"$badging" | head -1)"
 [ -n "$code" ] && [ -n "$name" ] || { echo "could not read version from $apk" >&2; exit 1; }
 
 # ---------------------------------------------------------------------------
-# 🔴 **A build does not ship without its release notes.**
+# A build does not ship without its release notes.
 #
 # The gate lives here, on the manifest, because the manifest is the step that
-# cannot be skipped — it is what the in-app updater reads, so an APK published
+# cannot be skipped, it is what the in-app updater reads, so an APK published
 # without it offers nobody an update. A reminder in a checklist would be
 # skipped on exactly the busy evening the notes matter most.
 #
-# ⚠️ It matches on `versionName` read out of the APK above, never on a number
+# It matches on `versionName` read out of the APK above, never on a number
 # typed here, for the same reason the manifest does: the two cannot disagree.
 #
 # The changelog lives in the relay repository because that is what serves the
-# page, and the check lives THERE too — see Scripts/covers-android.py. Parsing
+# page, and the check lives THERE too, see Scripts/covers-android.py. Parsing
 # the JSON here would leave a second copy of the schema to drift.
 if [ "${FN_SKIP_RELEASE_NOTES:-}" = "1" ]; then
   # Loud, and on stderr: a skipped gate that printed nothing would be a gate
   # nobody remembered turning off.
-  echo "⚠️  FN_SKIP_RELEASE_NOTES=1 — writing a manifest for $name with no" >&2
+  echo "FN_SKIP_RELEASE_NOTES=1, writing a manifest for $name with no" >&2
   echo "    release notes. Nothing on /releases will mention this build." >&2
 else
   relay_dir="${FN_RELAY_DIR:-$(cd "$(dirname "$0")/../.." && pwd)/flamenet-relay}"
@@ -68,7 +68,7 @@ without a word to anyone about what changed in it.
 Add a release to:
   $relay_dir/Resources/releases.json
 
-The newest release goes FIRST in the list, and it looks like this — write the
+The newest release goes FIRST in the list, and it looks like this, write the
 notes for somebody holding a phone, and put anything only an operator cares
 about in "selfHosting" at the end:
 
@@ -83,7 +83,7 @@ about in "selfHosting" at the end:
 
 "kind" is "new", "changed" or "fixed". Add an { "name": "ios", "version": … }
 or { "name": "relay" } entry alongside it when the same release touched those
-too — one release, every platform it landed on.
+too, one release, every platform it landed on.
 
 Then deploy the relay so the page and the APK go out together.
 MSG
@@ -93,9 +93,9 @@ fi
 
 sha="$(shasum -a 256 "$apk" | cut -d' ' -f1)"
 
-# ⚠️ No `url` field, deliberately. The client builds the download URL from the
+# No `url` field, deliberately. The client builds the download URL from the
 # relay it is signed in to and ignores anything the manifest says about where
-# the APK lives — a relay that could name the host could hand its users a
+# the APK lives, a relay that could name the host could hand its users a
 # different app. Adding one here would be dead weight at best and a trap for
 # the next person to implement a client at worst.
 cat <<JSON