feat(registers): deep‑linkable search via ?q=; docs: add docs/ and update README

- Register Explorer:
  - Sync search input with URL query param `q` for shareable deep links
  - Initialize search from `q` on load; update URL on input; remove `q` when cleared
  - Implemented with Next.js `useSearchParams`, `useRouter`, `usePathname`
  - File: src/app/registers/RegisterBrowser.tsx

- Documentation:
  - Add docs/ hub and initial guides
    - docs/index.md (docs index)
    - docs/getting-started.md (install/dev/build/start/lint/deploy)
    - docs/architecture.md (structure, theming, styling, key paths, scripts)
    - docs/registers.md (Register Explorer overview, search, deep links, implementation notes)
  - Rewrite README.md with project overview, features, quick start, scripts, and links to docs

Notes:
- Dev server uses port 4000 (Turbopack) via package.json
- Example deep link: /registers?q=vram

Date: 2025-12-11 13:11 (Junie@lucy.xalior.com)

docs/index.md

@@ -0,0 +1,9 @@
+# Spectrum Next Explorer — Documentation
+
+Welcome to the Spectrum Next Explorer docs. This site provides an overview of the project, how to develop and contribute, and details about key features like the Register Explorer and its search/deep‑linking capability.
+
+- Getting Started: ./getting-started.md
+- Architecture: ./architecture.md
+- Register Explorer: ./registers.md
+
+If you’re browsing on GitHub, the main README also links to these documents.