Pin rlcr-stop-gate project root at every wrapper testsite

tests/test-stop-hook-bg-allow.sh invokes rlcr-stop-gate.sh at four
spots (AC-9, AC-10c, AC-22, AC-22b). The wrapper resolves its
project root as `${CLAUDE_PROJECT_DIR:-$(pwd)}`, giving the env
var precedence over `cd`. When the outer runner exports
CLAUDE_PROJECT_DIR (the normal case in hosted environments),
those four tests were inspecting the outer repo instead of their
per-test fixtures, falling through with "ALLOW: stop gate
passed." and causing the suite to go red inside
tests/run-all-tests.sh.

Reproduced directly:

  CLAUDE_PROJECT_DIR=/tmp/outer-unrelated \
    bash tests/test-stop-hook-bg-allow.sh
  ...
  FAIL: AC-10c
  FAIL: AC-22

Fix: pass `--project-root "$FIXTURE_REPO"` at every wrapper call
site. The wrapper priority order is explicit flag >
CLAUDE_PROJECT_DIR env > cwd, so the gate now pins deterministically
to each fixture regardless of inherited environment.

No product-code change.

Validation:

  - bash tests/test-stop-hook-bg-allow.sh -> 39 passed, 0 failed
  - bash tests/run-all-tests.sh -> 1718 passed, 0 failed
  - CLAUDE_PROJECT_DIR=/tmp/outer-unrelated bash
    tests/test-stop-hook-bg-allow.sh -> 39 passed, 0 failed
  - HOME=/nonexistent/readonly bash tests/test-stop-hook-bg-allow.sh
    -> 39 passed, 0 failed
  - TZ=America/Los_Angeles bash tests/test-stop-hook-bg-allow.sh
    -> 39 passed, 0 failed
  - TZ=Asia/Tokyo bash tests/test-stop-hook-bg-allow.sh
    -> 39 passed, 0 failed

systemMessage wording unchanged. Version stays at 1.16.0.

Author: SihaoLiu

tests/test-stop-hook-bg-allow.sh

@@ -476,10 +476,12 @@ AC9_RESULT=$(emit_async_agent_launch_result "toolu_G" "agent_pending_G")
 write_transcript "$AC9_TRANSCRIPT" "$AC9_LAUNCH" "$AC9_RESULT"
 
 AC9_OUT="$AC9_REPO/gate-out.txt"
+# Pass --project-root explicitly so an inherited CLAUDE_PROJECT_DIR
+# from the outer runner cannot redirect the gate to the outer repo.
 set +e
 (
     cd "$AC9_REPO"
-    "$GATE_SCRIPT" --transcript-path "$AC9_TRANSCRIPT"
+    "$GATE_SCRIPT" --project-root "$AC9_REPO" --transcript-path "$AC9_TRANSCRIPT"
 ) > "$AC9_OUT" 2>&1
 AC9_EXIT=$?
 set -e
@@ -561,7 +563,9 @@ AC10C_OUT="$TEST_DIR/ac10c-out.txt"
 set +e
 (
     cd "$AC10C_REPO"
-    HOME="$FAKE_HOME" "$GATE_SCRIPT" --transcript-path "$AC10C_TILDE_PATH"
+    HOME="$FAKE_HOME" "$GATE_SCRIPT" \
+        --project-root "$AC10C_REPO" \
+        --transcript-path "$AC10C_TILDE_PATH"
 ) > "$AC10C_OUT" 2>&1
 AC10C_EXIT=$?
 set -e
@@ -1307,7 +1311,7 @@ AC22_OUT="$TEST_DIR/ac22-out.txt"
 set +e
 (
     cd "$AC22_REPO"
-    "$GATE_SCRIPT" --transcript-path "$AC22_TRANSCRIPT"
+    "$GATE_SCRIPT" --project-root "$AC22_REPO" --transcript-path "$AC22_TRANSCRIPT"
 ) > "$AC22_OUT" 2>&1
 AC22_EXIT=$?
 set -e
@@ -1362,7 +1366,7 @@ AC22B_OUT="$TEST_DIR/ac22b-out.txt"
 set +e
 (
     cd "$AC22B_REPO"
-    "$GATE_SCRIPT"
+    "$GATE_SCRIPT" --project-root "$AC22B_REPO"
 ) > "$AC22B_OUT" 2>&1
 AC22B_EXIT=$?
 set -e