fix(plugin): enforce gitignore for .ai-dlc/worktrees before worktree creation

Split worktree setup into two explicit steps with a guard to prevent
creating worktrees without gitignoring the directory first.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jwaldrip

plugin/skills/elaborate/SKILL.md

@@ -215,22 +215,36 @@ Continue asking until you can articulate back to the user, in your own words, ex
 
 Before beginning technical exploration, create the intent worktree and initialize the discovery scratchpad inside it. Creating the worktree early ensures **no artifacts are left on `main`** — all files from this point forward are written on the intent branch.
 
+**CRITICAL — Step 1: Gitignore worktrees directory (MUST run before creating any worktree)**
+
+You MUST ensure `.ai-dlc/worktrees/` is in `.gitignore` BEFORE creating the worktree. Run this as a **separate Bash command** first:
+
 ```bash
-# Derive intent slug from the user's description (same slug used throughout elaboration)
-INTENT_SLUG="{intent-slug}"
 PROJECT_ROOT=$(git rev-parse --show-toplevel)
-INTENT_BRANCH="ai-dlc/${INTENT_SLUG}/main"
-INTENT_WORKTREE="${PROJECT_ROOT}/.ai-dlc/worktrees/${INTENT_SLUG}"
-
-# Ensure worktrees directory exists and is gitignored (on main, before creating worktree)
 mkdir -p "${PROJECT_ROOT}/.ai-dlc/worktrees"
 if ! grep -q '\.ai-dlc/worktrees/' "${PROJECT_ROOT}/.gitignore" 2>/dev/null; then
   echo '.ai-dlc/worktrees/' >> "${PROJECT_ROOT}/.gitignore"
   git add "${PROJECT_ROOT}/.gitignore"
   git commit -m "chore: gitignore .ai-dlc/worktrees"
 fi
+```
+
+**Step 2: Create the intent worktree**
+
+Only after confirming the gitignore entry exists:
+
+```bash
+INTENT_SLUG="{intent-slug}"
+PROJECT_ROOT=$(git rev-parse --show-toplevel)
+INTENT_BRANCH="ai-dlc/${INTENT_SLUG}/main"
+INTENT_WORKTREE="${PROJECT_ROOT}/.ai-dlc/worktrees/${INTENT_SLUG}"
+
+# Guard: abort if worktrees dir is not gitignored
+if ! grep -q '\.ai-dlc/worktrees/' "${PROJECT_ROOT}/.gitignore" 2>/dev/null; then
+  echo "ERROR: .ai-dlc/worktrees/ is not in .gitignore. Run Step 1 first." >&2
+  exit 1
+fi
 
-# Create the intent worktree on its own branch
 git worktree add -B "$INTENT_BRANCH" "$INTENT_WORKTREE"
 cd "$INTENT_WORKTREE"
 ```