fix(shell): remove test harness pipe hazards

packages/mosaic/framework/tools/git/test-issue-comment-readback.sh

@@ -280,7 +280,10 @@ print("201")
 print(json.dumps(record))
 PY
 )
-    write_response "$(printf '%s' "$result" | head -n1)" "$(printf '%s' "$result" | tail -n +2)"
+    response_status="${result%%$'\n'*}"
+    response_body=""
+    [[ "$result" == *$'\n'* ]] && response_body="${result#*$'\n'}"
+    write_response "$response_status" "$response_body"
 elif [[ "$method" == "GET" && "$path" == "$ISSUE_COMMENT_API_BASE"/issues/comments/* ]]; then
     result=$(ISSUE_COMMENT_GET_ID="${path##*/}" python3 - <<'PY'
 import json
@@ -299,7 +302,10 @@ else:
     print(json.dumps(match))
 PY
 )
-    write_response "$(printf '%s' "$result" | head -n1)" "$(printf '%s' "$result" | tail -n +2)"
+    response_status="${result%%$'\n'*}"
+    response_body=""
+    [[ "$result" == *$'\n'* ]] && response_body="${result#*$'\n'}"
+    write_response "$response_status" "$response_body"
 else
     echo "Unexpected curl request: $method $url" >&2
     exit 97

packages/mosaic/framework/tools/git/test-lane-brief-pr-linkage.sh

@@ -69,7 +69,7 @@ section_nums() { # $1 = output  $2 = header-prefix
 }
 
 fail() { echo "FAIL: $1" >&2; exit 1; }
-contains() { printf '%s\n' "$1" | grep -qx "$2"; }
+contains() { grep -qx "$2" <<<"$1"; }
 
 # ---------------------------------------------------------------------------
 # Fixed (current) script behavior

packages/mosaic/framework/tools/git/test-pr-review-gitea-comment.sh

@@ -225,7 +225,10 @@ write_response() {
 emit() {
     # Split a two-line "status\n<json body>" python result into the response.
     local result="$1"
-    write_response "$(printf '%s' "$result" | head -n1)" "$(printf '%s' "$result" | tail -n +2)"
+    response_status="${result%%$'\n'*}"
+    response_body=""
+    [[ "$result" == *$'\n'* ]] && response_body="${result#*$'\n'}"
+    write_response "$response_status" "$response_body"
 }
 
 mode="${PR_REVIEW_TEST_MODE:-}"

packages/mosaic/framework/tools/git/test-pr-review-repo-host-override.sh

@@ -222,8 +222,8 @@ grep -q 'Unknown action: bogus-action' "$OUTPUT_FILE"
 
 # --- Case 2: -h/--help documents both overrides.
 HELP_TEXT="$("$SCRIPT_DIR/pr-review.sh" -h)"
-echo "$HELP_TEXT" | grep -q -- '-r, --repo'
-echo "$HELP_TEXT" | grep -q -- '-H, --host'
+grep -q -- '-r, --repo' <<<"$HELP_TEXT"
+grep -q -- '-H, --host' <<<"$HELP_TEXT"
 
 # --- Case 3 (comment): a TRUE no-git-origin dir + -r/-H must not silently die
 # and must not fail with "not a git repository or no origin remote" either.