Review company practice case studies and add source-backed updates

Background

The company practice section is valuable because it connects public engineering practices to concrete team decisions. It should stay source-backed and practical.

Scope

Review 10-company-practices/ for:

• Source freshness
• Broken or outdated references
• Overly broad claims
• Missing links back to theme guides
• Opportunities to add small, practical decision notes

Priority cases:

• Google Code Review
• Shopify Merge Queue
• Microsoft Release Flow
• Meta Sapling
• Microsoft Scalar
• Slack Deploys

Done When

• Case studies clearly link to original sources.
• Claims are framed as lessons or references, not universal rules.
• Related handbook articles are linked where useful.
• python3 scripts/check-docs.py passes.