Add local Vale KB style rules (NetwrixKB)

[hilram7]

Summary

• Creates a new Vale style, NetwrixKB, scoped exclusively to docs/kb/**/*.md
• Activates the style in .vale.ini, replacing the previous empty BasedOnStyles = that disabled all Vale checking on KB files
• KB files now receive KB-specific rules only — the Netwrix style is intentionally excluded to avoid a direct conflict (Netwrix promotes contractions; KB requires writing them out in full)

Changes

• .vale.ini — updated [docs/kb/**/*.md] section from BasedOnStyles = to BasedOnStyles = NetwrixKB
• .vale/styles/NetwrixKB/Contractions.yml — flags contractions (don't, can't, it's, etc.) and prompts writing them out in full; opposite direction from Netwrix.Contractions
• .vale/styles/NetwrixKB/HeadingCase.yml — enforces Chicago-style title case for all headings
• .vale/styles/NetwrixKB/FirstPersonPlural.yml — adapted from Netwrix style
• .vale/styles/NetwrixKB/Please.yml — adapted from Netwrix style
• .vale/styles/NetwrixKB/NoteThat.yml — adapted from Netwrix style; message updated to reference KB blockquote callouts (> NOTE:) instead of Docusaurus admonitions
• .vale/styles/NetwrixKB/WeakLinkText.yml — adapted from Netwrix style
• .vale/styles/NetwrixKB/ImpersonalFiller.yml — adapted from Netwrix style
• .vale/styles/NetwrixKB/Utilize.yml — adapted from Netwrix style

Testing

All tests sucessful and run locally with Vale 3.14.1.

• Contractions fires on KB file — NetwrixKB.Contractions flagged it's in docs/kb/threatmanager/integration-and-event-collection/no-threats-detected-despite-web-console-reporting-events.md
• HeadingCase fires on KB file — NetwrixKB.HeadingCase flagged a lowercase heading in docs/kb/privilegesecurediscovery/authentication-and-access/saml-assertion-not-yet-valid.md
• WeakLinkText fires on KB file — NetwrixKB.WeakLinkText flagged Learn more in the WinRM troubleshooting article (note: one known false positive — rule catches "Learn more" in body text, not just link text; same limitation exists in Netwrix.WeakLinkText)
• Netwrix rules do NOT fire on KB files — no Netwrix.Contractions warning appeared on the WinRM article despite containing "do not"; KB files are correctly isolated to NetwrixKB only
• NetwrixKB rules do NOT fire on docs files — docs/privilegesecure/4.2/admin/configuration/integrationconnector/integrationbyov/byovconnectorconfig.md
  returned 17 Netwrix.* warnings and zero NetwrixKB.* warnings

Notes

• This PR covers local usage only — CI autofix for KB files (vale-autofix-kb.yml) is a separate follow-up
• Contributors can run vale from the repo root after installing Vale (brew install vale + vale sync)