Inspired by Claude Code v2.1.199 (July 2, 2026): stacked slash-skill
invocations load all leading skills (up to 5), not just the first.
- agent/skill_commands.py: split_stacked_skill_commands() consumes leading
/skill tokens (stops at the first non-skill token so slash-path arguments
are never swallowed); build_stacked_skill_invocation_message() composes
the multi-skill turn reusing the existing bundle scaffolding markers so
extract_user_instruction_from_skill_message() keeps memory providers
storing the user's instruction, not N skill bodies.
- cli.py + gateway/run.py: dispatch the stacked path on both surfaces.
- 11 new tests + docs section in skills.md.