Add root README.md

Simple README covering the crate list, the `package = "runi-core"`
alias pattern for the clean `runi::` namespace, and pointers to the
book and docs.rs.

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

Author: xerial

README.md

@@ -0,0 +1,55 @@
+# Runi
+
+A curated collection of small, composable Rust libraries for building
+reliable infrastructure and CLI tools. Each crate is scoped to a
+single concern and can be used on its own or combined with the rest
+of the set.
+
+## Crates
+
+| Crate        | Role                                              |
+| ------------ | ------------------------------------------------- |
+| `runi-core`  | Foundation types (`Error`, `Result`, `Config`) + feature-gated bundle that re-exports the rest |
+| `runi-log`   | Structured logging with a Uni-style terminal format |
+| `runi-cli`   | CLI parser and terminal styling helpers           |
+| `runi-test`  | Test utilities (`rstest`, `pretty_assertions`, `proptest`) |
+
+## Quick start
+
+Most callers only need `runi-core` — it re-exports the others behind
+feature flags. Cargo's `package = "..."` alias lets you reach
+everything through the clean `runi::` namespace:
+
+```toml
+[dependencies]
+runi = { package = "runi-core", version = "0.1" }                           # + logging (default)
+runi = { package = "runi-core", version = "0.1", features = ["cli"] }      # + CLI helpers
+runi = { package = "runi-core", version = "0.1", default-features = false } # foundation only
+```
+
+```rust
+use runi::{Error, Result};
+use runi::log;
+use runi::cli::Tint;
+
+fn main() -> Result<()> {
+    log::init();
+    log::info!("hello from runi");
+    Ok(())
+}
+```
+
+Each sub-crate is also published standalone on crates.io if you
+prefer narrower dependencies.
+
+## Documentation
+
+- Book: <https://wvlet.github.io/runi>
+- API reference: [docs.rs/runi-core](https://docs.rs/runi-core),
+  [docs.rs/runi-log](https://docs.rs/runi-log),
+  [docs.rs/runi-cli](https://docs.rs/runi-cli),
+  [docs.rs/runi-test](https://docs.rs/runi-test)
+
+## License
+
+Apache-2.0