fix: parse lowercase 'archived' frontmatter field

The frontend writes 'archived: true' (lowercase) via handleUpdateFrontmatter,
but the Rust parser only recognized 'Archived' (titlecase). This caused all
notes archived from within Laputa to be read back as not archived — they
continued appearing in the sidebar and note list after restart.

Fix: add alias = "archived" to the serde attribute, matching the pattern
already used for 'trashed'/'Trashed'.

Regression tests added for both lowercase and titlecase variants.

src-tauri/src/vault/mod.rs

@@ -108,7 +108,7 @@ struct Frontmatter {
     owner: Option<String>,
     #[serde(rename = "Cadence")]
     cadence: Option<String>,
-    #[serde(rename = "Archived")]
+    #[serde(rename = "Archived", alias = "archived")]
     archived: Option<bool>,
     #[serde(rename = "Trashed", alias = "trashed")]
     trashed: Option<bool>,
@@ -1374,6 +1374,28 @@ Company: Acme Corp
         );
     }
 
+    #[test]
+    fn test_parse_archived_lowercase_alias() {
+        let dir = TempDir::new().unwrap();
+        let content = "---\narchived: true\n---\n# Old Quarter\n";
+        let entry = parse_test_entry(&dir, "old-quarter.md", content);
+        assert!(
+            entry.archived,
+            "lowercase 'archived' must be parsed via alias (frontend writes lowercase)"
+        );
+    }
+
+    #[test]
+    fn test_parse_archived_titlecase() {
+        let dir = TempDir::new().unwrap();
+        let content = "---\nArchived: true\n---\n# Old Quarter\n";
+        let entry = parse_test_entry(&dir, "old-quarter-2.md", content);
+        assert!(
+            entry.archived,
+            "titlecase 'Archived' must also be parsed"
+        );
+    }
+
     #[test]
     fn test_trashed_false_when_absent() {
         let dir = TempDir::new().unwrap();