Discord-first adapter for DeepSeek Harness

Key features

• Mention-driven sessions — an authorized @bot in a bound channel anchors a thread (your message becomes the first post), creates the DSH session, and submits the prompt at most once.
• The settings card is the first-run onboarding surface: the token entry writes the credential service's DSH_DISCORD_BOT_TOKEN ref over the plugin management channel, then triggers the start chain.
• Follow-ups inside the thread queue without a mention.
• Attached images ride alongthey are downloaded from the Discord CDN within strict size/host bounds and submitted as image parts for multimodal models.
• Stream rendering — typing indicator, one head message edited in place, per-tool activity rows, fenced long-answer splitting, one-time finalize