fix(copy): tighten the integrations, brand and trademark copy

[datlechin]

• Brand guidelines: shorter sentences, repeated rules removed, no nested lists. Rules, pins and anchors unchanged.
• Terms #trademarks: same meaning, plainer wording. Locales unchanged.
• Integrations UI, all 12 locales: built-in install button reads "Read the setup guide", the host button "Read the {host} docs", the docs link "Read the docs", the app filter "All apps".
• brand.json: shorter glyph description.
• README, CONTRIBUTING, LICENSE-CONTENT: plainer trademark lines. The scripts/brand-kit.sh example now shows its required argument.
• Registry text is in fix: plainer text for the built-in entries integrations#6 (merged). No summary changed, so no merge order. The next sync PR brings the new descriptions.