fix(tools/git): -h/--help now exits 0 across 7 wrappers (#701)

usage() hard-coded exit 1, so every --help/-h invocation on
issue-assign, issue-create, issue-list, milestone-create, pr-create,
pr-list, and pr-merge exited nonzero, logging phantom isError records
across fleet lanes and breaking set -e composition. usage() now takes
an exit-code arg (default 1); the -h|--help case calls usage 0. All
other error paths are untouched.

Closes #701

packages/mosaic/framework/tools/git/test-help-exit-code.sh

@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+# Regression harness for #701: -h/--help must exit 0, bad args must still exit nonzero.
+#
+# Covers the 7 wrappers whose usage() previously hard-coded `exit 1`, so every
+# --help invocation exited nonzero and logged a phantom isError across fleet lanes.
+# Asserts, per wrapper:
+#   1. `--help` exits 0 and prints usage.
+#   2. `-h` exits 0 and prints usage.
+#   3. A genuine unknown flag still exits nonzero (usage() default path untouched).
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+WRAPPERS=(
+    issue-assign.sh
+    issue-create.sh
+    issue-list.sh
+    milestone-create.sh
+    pr-create.sh
+    pr-list.sh
+    pr-merge.sh
+)
+
+fail=0
+
+for wrapper in "${WRAPPERS[@]}"; do
+    path="$SCRIPT_DIR/$wrapper"
+
+    if ! output=$(bash "$path" --help 2>&1); then
+        echo "FAIL: $wrapper --help exited nonzero" >&2
+        fail=1
+    elif [[ "$output" != Usage:* ]]; then
+        echo "FAIL: $wrapper --help did not print usage" >&2
+        fail=1
+    fi
+
+    if ! bash "$path" -h >/dev/null 2>&1; then
+        echo "FAIL: $wrapper -h exited nonzero" >&2
+        fail=1
+    fi
+
+    if bash "$path" --this-is-not-a-real-flag >/dev/null 2>&1; then
+        echo "FAIL: $wrapper accepted an unknown flag (should have exited nonzero)" >&2
+        fail=1
+    fi
+done
+
+if [[ "$fail" -eq 0 ]]; then
+    echo "help-exit-code regression passed (7/7 wrappers)"
+fi
+
+exit "$fail"