phase 0: scaffold workspace, plugin layout, and CI

Lay down the empty repo skeleton defined in SPEC.md §5 so subsequent
phases have somewhere to land:

- Cargo workspace (resolver v2, edition 2021, MSRV 1.83) with
  nuwiki-core, nuwiki-lsp, nuwiki-ls — dep direction matches §6.2.
- Vim/Neovim plugin directory layout (plugin, lua, autoload, ftdetect,
  ftplugin, syntax, doc, scripts) with header-only stubs.
- .gitea/workflows/ci.yaml running fmt, clippy -D warnings, and tests
  pinned to Rust 1.83.
- README, dual MIT/Apache-2.0 license texts, .gitignore.

Verified: cargo check / fmt --check / clippy / test all clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -0,0 +1,48 @@
+# nuwiki
+
+A Vim/Neovim plugin providing full vimwiki syntax support, implemented as a
+Rust-based language server (LSP).
+
+> **Status:** Phase 0 — scaffolding. Not yet functional.
+
+See [`SPEC.md`](./SPEC.md) for the full project specification.
+
+## Repository layout
+
+```
+nuwiki/
+├── Cargo.toml              workspace root
+├── crates/
+│   ├── nuwiki-core/        parser, AST, renderer (no editor deps)
+│   ├── nuwiki-lsp/         LSP protocol bridge
+│   └── nuwiki-ls/          binary that speaks LSP over stdio
+├── plugin/                 universal Vim/Neovim entry point
+├── lua/nuwiki/             Neovim Lua glue
+├── autoload/nuwiki/        Vim VimL glue
+├── ftdetect/               filetype detection for .wiki
+├── ftplugin/               per-buffer filetype settings
+├── syntax/                 static fallback highlighting
+├── doc/                    `:h nuwiki`
+├── scripts/                build-time helpers
+└── .gitea/workflows/       CI / release pipelines
+```
+
+## Building
+
+```sh
+cargo build --workspace
+cargo test  --workspace
+```
+
+MSRV: Rust 1.83.
+
+## License
+
+Dual-licensed under either of:
+
+- Apache License, Version 2.0 ([`LICENSE-APACHE`](./LICENSE-APACHE))
+- MIT license ([`LICENSE-MIT`](./LICENSE-MIT))
+
+at your option. Unless you explicitly state otherwise, any contribution
+intentionally submitted for inclusion in this work shall be dual licensed as
+above, without any additional terms or conditions.