docs: update 6-3-contracts.md

[habib424]

Drafted by Ship Ship 🚢 — confidence 🟢 high

What changed

Added a brief subsection explaining the Total Contract Value display toggle (Net vs Gross) that appears on the contract detail view. The toggle is accessible via a small edit icon on the TCV stat card and is a company-wide setting that affects how contract values are displayed across all contracts.

Source PRs

• light#7314 — feat(INTE-164): net/gross toggle for total contract value
• axolotl#4508 — feature: add net/gross toggle for total contract value

How to use this PR

1. Review the diff against the existing article — focus on accuracy and customer voice.
2. Merge if it reads well. Edit and push to this branch if it needs adjustment.
3. Close without merging if the article doesn't actually need this update.

Once we have a track record of clean drafts, we'll graduate to auto-merge with a delay buffer. For now: human-in-the-loop.