fix(glmt): resolve thinking block signature timing race

- guard against empty content in _createSignatureDeltaEvent()

- consolidate debug flags: CCS_DEBUG_LOG, CCS_GLMT_DEBUG → CCS_DEBUG

- add 6 regression tests for signature race condition

- update docs with simplified debug flag usage

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@kaitranntt/ccs",
-  "version": "3.4.4",
+  "version": "3.4.5",
   "description": "Claude Code Switch - Instant profile switching between Claude Sonnet 4.5 and GLM 4.6",
   "keywords": [
     "cli",