All apps: a second launch hands its files to the running copy

R4.12 (user report). The copy holding the instance lock opens a local
door guarded by a random token in its data folder; a second copy sends
its file paths there, lets it take the foreground, and exits 0 instead
of showing "already running". Files join the ely_ui::on_open queue every
app already uses; the main window comes to the front. Also records the
R4.10 round 1 verdict.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/scripts/one-instance.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# A second ElyDoc is refused; the first keeps its data.
+# A second ElyDoc hands its file over and ends.
 set -euo pipefail
 
 root=$(cd "$(dirname "$0")/../.." && pwd)
@@ -18,7 +18,7 @@ trap cleanup EXIT
 fail() { echo "FAIL: $*" >&2; exit 1; }
 
 cargo build -q -p ely-lok --bins -p ely-doc --manifest-path "$root/Cargo.toml"
-run() { HOME="$work/home" ELY_LOG=info ELY_LOCALE=en ELY_NO_DIALOG=1 ELY_SMOKE=hold exec "$root/target/debug/ely-doc"; }
+run() { HOME="$work/home" ELY_LOG=info ELY_LOCALE=en ELY_NO_DIALOG=1 ELY_SMOKE=hold exec "$root/target/debug/ely-doc" "$@"; }
 run >"$work/first" 2>&1 &
 pid=$!
 for _ in $(seq 90); do grep -q "lok: first tile drawn" "$work/first" && break; sleep 1; done
@@ -26,10 +26,11 @@ grep -q "lok: first tile drawn" "$work/first" || fail "the first copy did not st
 data="$work/home/Library/Application Support/ElyOffice/ely-doc"
 [ -d "$data/work" ] || fail "no work folder"
 touch "$data/work/kept"
-status=0
-(run) >"$work/second" 2>&1 || status=$?
-[ "$status" != 0 ] || fail "the second copy started"
-grep -q "already running (process $pid)" "$work/second" || fail "the refusal: $(tail -3 "$work/second")"
+cp "$root/tests/fixtures/office/t.docx" "$work/handed.docx"
+(run "$work/handed.docx") >"$work/second" 2>&1 || fail "the second copy failed: $(tail -3 "$work/second")"
+for _ in $(seq 30); do grep -q "opened handed.docx as tab" "$work/first" && break; sleep 1; done
+grep -q "another copy handed over 1 files" "$work/first" || fail "no hand-over: $(tail -5 "$work/first")"
+grep -q "opened handed.docx as tab" "$work/first" || fail "the first copy did not open it: $(tail -5 "$work/first")"
 [ -e "$data/work/kept" ] || fail "the second copy wiped the first's work folder"
 kill -0 "$pid" || fail "the first copy died"
-echo "ok: a second ElyDoc is refused and the first keeps its data"
+echo "ok: a second ElyDoc hands its file to the first, which keeps its data"