Fix runtime model detection using script path instead of CLAUDE_PLUGIN_ROOT

CLAUDE_PLUGIN_ROOT is a config-time template variable that Claude Code
substitutes when loading plugin configs, not a runtime environment
variable. The previous check always evaluated to false, causing
gpt-5.2 to be selected even in plugin mode. Use BASH_SOURCE path to
detect if the script runs from .claude/plugins/cache/ instead.

Author: SihaoLiu

hooks/lib/loop-common.sh

@@ -43,14 +43,19 @@ readonly FIELD_AGENT_TEAMS="agent_teams"
 # Both use :- so scripts can override before sourcing (e.g. PR loop sets different model/effort).
 #
 # Runtime-aware model selection:
-# - Claude Code plugin flow (CLAUDE_PLUGIN_ROOT set) -> gpt-5.3-codex
-# - Skill mode (Codex/Kimi, no CLAUDE_PLUGIN_ROOT)  -> gpt-5.2
+# Detect Claude Code plugin mode by checking if this script lives under
+# .claude/plugins/cache/ (CLAUDE_PLUGIN_ROOT is a config-time template
+# variable, not a runtime env var, so we cannot check it directly).
+#   - Claude Code plugin mode -> gpt-5.3-codex
+#   - Skill mode (Codex/Kimi) -> gpt-5.2
 if [[ -z "${DEFAULT_CODEX_MODEL:-}" ]]; then
-    if [[ -n "${CLAUDE_PLUGIN_ROOT:-}" ]]; then
+    _LOOP_COMMON_SELF="${BASH_SOURCE[0]:-$0}"
+    if [[ "$_LOOP_COMMON_SELF" == */.claude/plugins/cache/* ]]; then
         DEFAULT_CODEX_MODEL="gpt-5.3-codex"
     else
         DEFAULT_CODEX_MODEL="gpt-5.2"
     fi
+    unset _LOOP_COMMON_SELF
 fi
 DEFAULT_CODEX_EFFORT="${DEFAULT_CODEX_EFFORT:-xhigh}"