Callcenter OS ADR-003 added: Boards + KPS settlement spine

BLUF: Captured the pivot that Mattermost Boards should become the lead/work operating surface, while kps-estimate/backend-go becomes the quote, margin, incentive wallet, and settlement engine.

Files changed:

• /home/tlswk/projects/callcenter-os/docs/2026-07-08-adr-003-mattermost-boards-kps-settlement.md
• /home/tlswk/projects/callcenter-os/README.md

Key decision:

• Boards cards represent leads/deals operationally.
• KPS Go pricing engine remains the money engine.
• Settlement is server-side, auditable, and append-only; Boards only shows non-sensitive operational projection.
• ADR-002 is revised, not discarded: owned cockpit remains for KPI, settlement admin, QA/STT review, permission-sensitive views, and partner dashboards.

Evidence referenced:

• Boards plugin models/API/websocket in /home/tlswk/projects/matter-center/mattermost-plugin-boards.
• KPS Go Compute/QuickQuote/pricing tests in /home/tlswk/projects/kps-estimate/backend-go.
• Existing frontend wallet prototype in kps-estimate/frontend/components/QuickQuote.tsx.

Next spike:

1. Create Callcenter Leads Boards template.
2. Add backend-go/internal/settlement with wallet calculation and zero-sum validation tests.
3. Add adapter endpoint to create quote snapshot, settlement draft/final result, and Boards card patch payload.
4. Patch one Boards card and post one Mattermost message.