feat: vault management — remove vault from list and restore Getting Started

Add ability to remove vaults from the app list without deleting files on disk,
and restore the bundled Getting Started demo vault when needed.

Changes:
- Rust: add hidden_defaults field to VaultList for tracking removed default vaults
- useVaultSwitcher: add removeVault() and restoreGettingStarted() with auto-switch
- useCommandRegistry: add 'Remove Vault from List' and 'Restore Getting Started Vault' commands
- StatusBar: add X button per vault item in vault menu dropdown
- 25 new tests covering removal, restore, edge cases, and command palette

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/vault_list.rs

@@ -12,6 +12,8 @@ pub struct VaultEntry {
 pub struct VaultList {
     pub vaults: Vec<VaultEntry>,
     pub active_vault: Option<String>,
+    #[serde(default)]
+    pub hidden_defaults: Vec<String>,
 }
 
 fn vault_list_path() -> Result<PathBuf, String> {
@@ -79,6 +81,7 @@ mod tests {
                 },
             ],
             active_vault: Some("/Users/luca/Laputa".to_string()),
+            hidden_defaults: vec![],
         };
         let loaded = save_and_reload(&list);
         assert_eq!(loaded.vaults.len(), 2);
@@ -116,6 +119,7 @@ mod tests {
                 path: "/tmp/test".to_string(),
             }],
             active_vault: None,
+            hidden_defaults: vec![],
         };
         save_at(&path, &list).unwrap();
         assert!(path.exists());
@@ -136,5 +140,35 @@ mod tests {
         let loaded = save_and_reload(&list);
         assert!(loaded.vaults.is_empty());
         assert!(loaded.active_vault.is_none());
+        assert!(loaded.hidden_defaults.is_empty());
+    }
+
+    #[test]
+    fn hidden_defaults_roundtrip() {
+        let list = VaultList {
+            vaults: vec![],
+            active_vault: None,
+            hidden_defaults: vec!["/Users/luca/Documents/Getting Started".to_string()],
+        };
+        let loaded = save_and_reload(&list);
+        assert_eq!(loaded.hidden_defaults.len(), 1);
+        assert_eq!(
+            loaded.hidden_defaults[0],
+            "/Users/luca/Documents/Getting Started"
+        );
+    }
+
+    #[test]
+    fn load_legacy_format_without_hidden_defaults() {
+        let dir = tempfile::TempDir::new().unwrap();
+        let path = dir.path().join("legacy.json");
+        // Simulate old format without hidden_defaults field
+        fs::write(
+            &path,
+            r#"{"vaults":[],"active_vault":null}"#,
+        )
+        .unwrap();
+        let loaded = load_at(&path).unwrap();
+        assert!(loaded.hidden_defaults.is_empty());
     }
 }