feat(fermata): add cargo publish/install metadata

Adds license (MIT OR Apache-2.0), repository (placeholder TODO URL),
readme, keywords, categories, rust-version, dual LICENSE files, and a
README install section. Adds a regression test asserting these fields
remain present so future edits cannot silently break cargo publish.

`cargo install --path crates/dirigent_fermata --features cli` produces
a working `fermata` binary; `cargo publish --dry-run` is clean.

Cargo.toml

@@ -2,7 +2,14 @@
 name = "dirigent_fermata"
 version = "0.1.0"
 edition = "2021"
+rust-version = "1.75"
 description = "Harness-agnostic policy gate for AI coding agents (.botignore + botignore.toml)"
+license = "MIT OR Apache-2.0"
+# TODO: replace with real URL before publish
+repository = "https://github.com/TODO/dirigent-fermata"
+readme = "README.md"
+keywords = ["ai", "agents", "security", "policy", "gitignore"]
+categories = ["command-line-utilities", "development-tools"]
 
 [lib]
 path = "src/lib.rs"