feat: tag derivation from ClaML metadata + validity

src/tags.rs

@@ -1 +1,12 @@
-// implemented in a later task
+use crate::model::{IcdMeta, Tags};
+
+/// Build display/filter Tags from ICD metadata and the Alpha-ID
+/// validity flag of the matched entry.
+pub fn tags_for(m: &IcdMeta, alpha_valid: bool) -> Tags {
+    Tags {
+        billable: m.para295 == "P",
+        valid: alpha_valid,
+        chapter: m.chapter.clone(),
+        exotic: m.exotic,
+    }
+}

tests/tags_tests.rs

@@ -0,0 +1,20 @@
+use alpha_id::model::IcdMeta;
+use alpha_id::tags::tags_for;
+
+#[test]
+fn billable_when_para295_is_p_and_valid() {
+    let mut m = IcdMeta::default();
+    m.para295 = "P".into();
+    m.chapter = "01".into();
+    let t = tags_for(&m, true);
+    assert!(t.billable);
+    assert!(t.valid);
+    assert_eq!(t.chapter, "01");
+}
+
+#[test]
+fn not_billable_when_para295_is_v() {
+    let mut m = IcdMeta::default();
+    m.para295 = "V".into();
+    assert!(!tags_for(&m, true).billable);
+}