Add promotion launch kit

[SonAIengine]

Summary

• add README/README.ko.md positioning section explaining why Synaptic is more than plain RAG
• add examples/launch_demo.py, a 60-second terminal demo over documents, SQL rows, retrieval feedback, and memory health metadata
• add docs/launch/demo_video.md with storyboard, captions, recording commands, and social copy for the video
• refresh the Show HN draft so it matches the current API, license, infra story, and memory operating layer
• add a promotion playbook with release copy, social posts, channel order, guardrails, and measurement backlog
• expand PyPI metadata links and package keywords for discoverability
• add GitHub issue forms for bug reports, feature requests, and Discussions routing

External repo setup

• enabled GitHub Discussions
• confirmed Issues are enabled
• kept current repo topics/description/homepage in place

Verification

• uv run ruff check .
• uv run synaptic-quickstart --json
• uv run python examples/launch_demo.py --no-pause
• pyproject metadata sanity check
• issue template YAML parse check
• launch-doc markdown fence check
• stale launch-doc pattern scan
• git diff --check