Add per-feature demos to examples/slack that narrate per-platform degradation
explicitly rather than failing silently:
- emoji triage — 🐛/🔥/✅ reactions file/escalate/ack via the agent
- /preview — ephemeral draft issue (native only-you on Slack, DM fallback on
Discord/Telegram)
- /file-issue — modal form (Slack rich, Discord text-only, Telegram
conversational fallback)
Also updates the Slack frontend guide (slack.mdx) with the capability matrix.
Alem Tuzlak