docs: add auto-generated config TOML reference

cot-test/Cargo.toml

@@ -18,12 +18,28 @@ cot-cli = { workspace = true, features = ["test_utils"] }
 cot.workspace = true
 glob.workspace = true
 libtest-mimic.workspace = true
+schemars = { workspace = true, features = ["std"] }
+serde_json.workspace = true
 thiserror.workspace = true
 
+[features]
+# Enables generating the configuration file reference (docs/configuration.md).
+config-docs = ["cot/config-docs"]
+
 [lints]
 workspace = true
 
 [[test]]
 name = "doc_code_blocks"
 path = "tests/doc_code_blocks.rs"
 harness = false
+
+[[test]]
+name = "config_reference"
+path = "tests/config_reference.rs"
+required-features = ["config-docs"]
+
+[[bin]]
+name = "generate_config_docs"
+path = "src/bin/generate_config_docs.rs"
+required-features = ["config-docs"]

cot-test/src/bin/generate_config_docs.rs

@@ -0,0 +1,20 @@
+//! Regenerates `docs/configuration.md` from `cot::config::ProjectConfig`'s type
+//! definition.
+//!
+//! Run via `just generate-config-docs`.
+
+use std::path::PathBuf;
+
+fn main() {
+    let content = cot_test::config_reference::generate_config_reference();
+
+    let manifest_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    let docs_path = manifest_dir
+        .parent()
+        .expect("failed to get workspace path")
+        .join("docs")
+        .join("configuration.md");
+
+    std::fs::write(&docs_path, content).expect("failed to write docs/configuration.md");
+    println!("Wrote {}", docs_path.display());
+}