fix(skill-author): resolve skill-audit findings

- script: new-skill.sh now exits 0 when target already exists (idempotent
  retry-safe) instead of exit 1; --help updated to reflect narrowed error cases
- test: updated bats test to assert success and "nothing to do" output
- body: removed speculative "Extract the skill from a real task" advice
  (human-targeted, not agent-actionable)
- formatting: converted H4 headings in Step 2 to bold text (H2/H3 two-tier model)
- provenance: removed orphan agentskills-llms-txt entry from references/sources.md;
  added discovery-only comment

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

plugins/kyberforge/skills/skill-author/scripts/new-skill.sh

@@ -20,8 +20,8 @@ Output:
   Creates <destination-dir>/<skill-name>/ with annotated templates ready to fill in.
 
 Exit codes:
-  0  Scaffold created successfully
-  1  Invalid arguments or destination already exists
+  0  Scaffold created successfully, or destination already exists (no-op)
+  1  Invalid arguments, missing destination parent, or templates not found
 EOF
 }
 
@@ -63,11 +63,10 @@ fi
 
 TARGET="$DEST_DIR/$SKILL_NAME"
 
-# Refuse to overwrite existing directory
+# Destination already exists — treat as a no-op so retries are safe
 if [[ -d "$TARGET" ]]; then
-  echo "Error: '$TARGET' already exists." >&2
-  echo "       Remove it first or choose a different name." >&2
-  exit 1
+  echo "Scaffold already exists at '$TARGET' — nothing to do." >&2
+  exit 0
 fi
 
 # Copy templates to destination