feat(wfe-yaml): add multi-workflow YAML and typed input/output schemas

YamlWorkflowFile supports both single (workflow:) and multi (workflows:)
formats. WorkflowSpec gains typed inputs/outputs declarations.
Type string parser for inline types ("string?", "list<number>", etc.).
load_workflow_from_str returns Vec<CompiledWorkflow>.
Backward-compatible load_single_workflow_from_str convenience function.

wfe-yaml/tests/types.rs

@@ -0,0 +1,107 @@
+use wfe_yaml::types::{parse_type_string, SchemaType};
+
+#[test]
+fn parse_all_primitives() {
+    assert_eq!(parse_type_string("string").unwrap(), SchemaType::String);
+    assert_eq!(parse_type_string("number").unwrap(), SchemaType::Number);
+    assert_eq!(parse_type_string("integer").unwrap(), SchemaType::Integer);
+    assert_eq!(parse_type_string("bool").unwrap(), SchemaType::Bool);
+    assert_eq!(parse_type_string("any").unwrap(), SchemaType::Any);
+}
+
+#[test]
+fn parse_optional_types() {
+    assert_eq!(
+        parse_type_string("string?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("integer?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::Integer))
+    );
+}
+
+#[test]
+fn parse_list_types() {
+    assert_eq!(
+        parse_type_string("list<string>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("list<number>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::Number))
+    );
+}
+
+#[test]
+fn parse_map_types() {
+    assert_eq!(
+        parse_type_string("map<string>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("map<any>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::Any))
+    );
+}
+
+#[test]
+fn parse_nested_generics() {
+    assert_eq!(
+        parse_type_string("list<list<string>>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+    );
+    assert_eq!(
+        parse_type_string("map<list<integer>>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::List(Box::new(SchemaType::Integer))))
+    );
+}
+
+#[test]
+fn parse_optional_generic() {
+    assert_eq!(
+        parse_type_string("list<string>?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+    );
+}
+
+#[test]
+fn parse_unknown_type_returns_error() {
+    let err = parse_type_string("foobar").unwrap_err();
+    assert!(err.contains("Unknown type"), "Got: {err}");
+}
+
+#[test]
+fn parse_unknown_generic_container_returns_error() {
+    let err = parse_type_string("set<string>").unwrap_err();
+    assert!(err.contains("Unknown generic type"), "Got: {err}");
+}
+
+#[test]
+fn parse_empty_returns_error() {
+    let err = parse_type_string("").unwrap_err();
+    assert!(err.contains("Empty"), "Got: {err}");
+}
+
+#[test]
+fn parse_malformed_generic_returns_error() {
+    let err = parse_type_string("list<string").unwrap_err();
+    assert!(err.contains("Malformed"), "Got: {err}");
+}
+
+#[test]
+fn display_roundtrip() {
+    for s in &[
+        "string",
+        "number",
+        "integer",
+        "bool",
+        "any",
+        "list<string>",
+        "map<number>",
+        "list<list<string>>",
+    ] {
+        let parsed = parse_type_string(s).unwrap();
+        assert_eq!(parsed.to_string(), *s, "Roundtrip failed for {s}");
+    }
+}