Add branching-strategy skill with next and create actions

Version-aware branch naming (X.Y.Z.Q/{TASK_CODE}-{FEATURE}-{SEQ}),
branch creation from origin/test with origin/main fallback, and the
PR-into-test merge rule. Ships a TypeScript CLI (next, create) plus
shell modules (loggers, base, cli) run via Taskfile.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/.scripts/base/lib/-ensure-environment-variable.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+# -------------------------------------------------------------------------------------
+#
+#
+#
+# -------------------------------------------------------------------------------------
+
+. ./.scripts/loggers/lib/--index-api.sh
+
+_base_ensureEnvironmentVariable() {
+  local FUNCTION_NAME="_base_ensureEnvironmentVariable"
+  local ENV_VAR_NAME="$1"
+  _loggers_info "${FUNCTION_NAME}" "ENV_VAR_NAME: ${ENV_VAR_NAME}"
+  if [ -z "${!ENV_VAR_NAME}" ]; then
+    _loggers_error "${FUNCTION_NAME}" "Missing required environment variable: ${ENV_VAR_NAME}. Check .env or .env-* files!"
+    exit 1
+  fi
+}