docs: deep implementation sections for 10 proposals (21-30)

[82deutschmark]

Adds long "Detailed Implementation Plan" sections to ten proposal docs:

• 21-expert-discovery-and-fit-scoring.md
• 22-multi-stage-verification-workflow.md
• 23-expert-collaboration-marketplace-and-reputation.md
• 24-cross-border-project-verification-framework.md
• 25-verification-incentives-governance-and-liability.md
• 26-news-intake-and-opportunity-sensing-grid.md
• 27-multi-angle-topic-verification-engine.md
• 28-autonomous-bid-factory-orchestration.md
• 29-elo-ranked-bid-selection-and-escalation.md
• 30-autonomous-bid-governance-risk-and-ethics.md

Each includes phased rollout, integration points, data model additions, safeguards, and validation checklists.