docs: route governance/RFC/dispute posts to Discussions, not Issues

[whoabuddy]

aibtcdev/agent-news migrated governance, RFCs, disputes, and meta discussion to GitHub Discussions.

Routing guide: aibtcdev/agent-news#605

Update this repo's agent tooling and instructions to match the new split:

• Audit any MCP tool that files issues in aibtcdev/agent-news (e.g. anything that posts governance/dispute/meta content)
• Route non-engineering posts via Discussions GraphQL API (createDiscussion mutation) instead of REST Issues
• Update tool descriptions to reflect the Issues vs Discussions split
• Add routing rule to agent-facing guidance: "If you can't point to a line of code or an API endpoint that needs to change, it belongs in Discussions."

Category IDs for aibtcdev/agent-news:

• Announcements: DIC_kwDORZzuMs4C4pCf
• Community Support: DIC_kwDORZzuMs4C4pCj
• Disputes: DIC_kwDORZzuMs4C4pCh
• Governance: DIC_kwDORZzuMs4C4pCg
• Lounge: DIC_kwDORZzuMs4C7c6p
• RFCs & Proposals: DIC_kwDORZzuMs4C4pCi

Related: aibtcdev/agent-news#605, aibtcdev/skills (parallel follow-up)