fix(agents-init): fix gitignore duplicate entries, add block comment style

- Strip leading / from pattern before git check-ignore so root-anchored
  patterns like /AGENTS.md are checked as repo-relative paths (AGENTS.md)
  and correctly match existing rules — fixes duplicates on every run
- Rework helper to accept multiple patterns and write them as a single
  labeled block with project-style header/footer comment rather than
  appending bare patterns one at a time
- Move gitignore calls out of per-plug loop in --plugins mode so all
  three docs/ patterns are checked and written in one block
- Remove 5 duplicate bare entries left in .gitignore by the broken runs

functions/agents-init.fish

@@ -208,9 +208,7 @@ function agents-init --description 'scaffold AGENTS/ sub-repo with agent spec fi
         end
 
         # ── .gitignore ────────────────────────────────────────────────────────
-        for pattern in "AGENTS/" "/AGENTS.md" "/CLAUDE.md"
-            _agents_init_ensure_gitignore "$root" "$pattern"
-        end
+        _agents_init_ensure_gitignore "$root" "agents-init --agents" "AGENTS/" "/AGENTS.md" "/CLAUDE.md"
     end
 
     #   ─────────────────────────── --plugins mode ──────────────────────────────
@@ -266,8 +264,8 @@ function agents-init --description 'scaffold AGENTS/ sub-repo with agent spec fi
                 echo "$c_ok→ Linked docs/$plug → AGENTS/plugins/$plug$c_reset"
             end
 
-            _agents_init_ensure_gitignore "$root" "docs/$plug"
         end
+        _agents_init_ensure_gitignore "$root" "agents-init --plugins" "docs/superpowers" "docs/plans" "docs/specs"
     end
 
     #   ──────────────────────── Auto-commit AGENTS/ ────────────────────────────