fix(skills): anchor guard/freeze/careful hook paths so they survive CC 2.1.162 (#1871)

The PreToolUse frontmatter hooks for guard, freeze, and careful invoked
`bash ${CLAUDE_SKILL_DIR}/.../check-*.sh`. Claude Code 2.1.162 no longer populates
${CLAUDE_SKILL_DIR} in the skill-hook execution env, so it expanded to empty and
every Edit/Write/Bash ran `bash /...` and errored — breaking the safety skills
entirely.

Frontmatter hooks run before any skill-body bash, so no runtime-resolved variable
can fix this; the command must be a path that's valid at hook time. Anchor to the
installed checkout: $HOME/.claude/skills/gstack/{careful,freeze}/bin/check-*.sh,
where the scripts actually live. ($HOME is expanded by the hook shell.)

Reported by @omariani-howdy. Regenerated the three SKILL.md from templates.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

careful/SKILL.md

@@ -14,7 +14,7 @@ hooks:
     - matcher: "Bash"
       hooks:
         - type: command
-          command: "bash ${CLAUDE_SKILL_DIR}/bin/check-careful.sh"
+          command: "bash $HOME/.claude/skills/gstack/careful/bin/check-careful.sh"
           statusMessage: "Checking for destructive commands..."
 ---
 <!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly -->

careful/SKILL.md.tmpl

@@ -19,7 +19,7 @@ hooks:
     - matcher: "Bash"
       hooks:
         - type: command
-          command: "bash ${CLAUDE_SKILL_DIR}/bin/check-careful.sh"
+          command: "bash $HOME/.claude/skills/gstack/careful/bin/check-careful.sh"
           statusMessage: "Checking for destructive commands..."
 sensitive: true
 ---