Resolve Groundwork styles from the installed peer dependency

[krowvin]

I went ahead and hotfixed the current overlap issue GWW had on the github pages site with
#353

This PR solves the larger issue of downstream repos needing to import both groundwork and style.css by bundling the two togetehr and only requiring you install the groundwork-water css exposed file. (See docs in PR changes)

Changes

• Resolve Groundwork CSS from the app's installed peer dependency instead of embedding an older copy, preventing docs content from covering the sticky header.
• Keep one Groundwork Water stylesheet import for both libraries. Preserve /style.css and /dist/style.css and remove the separate docs import.
• Document the required import, migration, and Groundwork ^4.3.2 compatibility. Add packed-consumer checks for Groundwork 4 and React 18/19.
• Major release: Groundwork 3 apps must upgrade or remain on Groundwork Water 4.x. The CSS entry requires a package-aware bundler, so direct browser/CDN stylesheet links must use bundled output.
• Related: Styling errors: gw seems to override gww styles USACE/groundwork#310, Use Groundwork 4 in docs #324, Use Groundwork 4.3.2 in docs #351, and USACE/mvp-wm-web#150. MVP's current-package fix remains independent of this release.

Testing

• Unit tests: 29 files, 204 tests passed.
• Local integration: library and docs production builds passed. Packed-consumer builds verified both CSS entry paths, search styles, and installed Groundwork header styles with Groundwork 4.3.2 and React 18/19.
• Local Playwright: docs homepage and /docs, plus a fixture search inside SiteWrapper, passed desktop/mobile checks at 1440px and 390px. Verified search empty/results states and header stacking after scrolling.
• Formatting and git diff --check: passed. Builds retain configuration, icon asset, directive, and bundle warnings. No deployed-site testing performed.

[LaurenAllin]

Changes seem to be working as expected. Noticed some other styling issues where components overlay the site-wrapper header. This shows up in the prod version of groundwork-water docs, however, so this is a separate issue.

[krowvin]

Should be fixed with #353

I had to run the manual deploy of the site this morning after we chatted!