tests: every test dir is removed when its test ends, pass or panic

Many test helpers removed their temp dir only before the test, or only
on pass, so runs left them behind: 117,000 filled /tmp (RAM here) and
stopped a mutation run. Each now holds a guard that removes the dir on
drop, unwind included; servers started on a test dir hold its guard
until they stop. A full cargo test --workspace leaves 0 dirs (859
before). just sweep-test-tmp stays for runs killed mid-test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-mcp/tests/spec_vault.rs

@@ -58,6 +58,9 @@ struct Mcp {
     validators: HashMap<String, jsonschema::Validator>,
     /// Every response line the server wrote, with the tool it answered.
     transcript: Vec<(String, String)>,
+    /// The books dir when the server owns it: removed after the server
+    /// stops (fields drop after `Drop::drop`).
+    books_dir: Option<TestDir>,
 }
 
 impl Drop for Mcp {
@@ -69,7 +72,35 @@ impl Drop for Mcp {
 
 static DIR_SEQ: AtomicU64 = AtomicU64::new(0);
 
-fn test_dir(name: &str) -> PathBuf {
+/// A test's dir and the folders beside it (`-inbox`, `-outside`),
+/// removed when the test ends, pass or panic.
+struct TestDir(PathBuf);
+
+impl std::ops::Deref for TestDir {
+    type Target = std::path::Path;
+    fn deref(&self) -> &std::path::Path {
+        &self.0
+    }
+}
+
+impl AsRef<std::path::Path> for TestDir {
+    fn as_ref(&self) -> &std::path::Path {
+        &self.0
+    }
+}
+
+impl Drop for TestDir {
+    fn drop(&mut self) {
+        let _ = std::fs::remove_dir_all(&self.0);
+        for beside in ["-inbox", "-outside"] {
+            let p = PathBuf::from(format!("{}{beside}", self.0.display()));
+            let _ = std::fs::remove_dir_all(&p);
+            let _ = std::fs::remove_file(&p);
+        }
+    }
+}
+
+fn test_dir(name: &str) -> TestDir {
     let n = DIR_SEQ.fetch_add(1, Ordering::Relaxed);
     let dir = std::env::temp_dir().join(format!(
         "ledger-mcp-spec-vault-{}-{name}-{n}",
@@ -77,7 +108,7 @@ fn test_dir(name: &str) -> PathBuf {
     ));
     let _ = std::fs::remove_dir_all(&dir);
     std::fs::create_dir_all(&dir).unwrap();
-    dir
+    TestDir(dir)
 }
 
 /// A directory beside the books dir `dir`, outside it: the vault key,
@@ -164,6 +195,7 @@ impl Mcp {
             }
         });
         let mut mcp = Self {
+            books_dir: None,
             stdin,
             rx,
             child,
@@ -402,6 +434,7 @@ fn books_with(name: &str, extra: &str) -> Mcp {
         json!({"vendor": "Acme Design", "form_1099": "nec"}),
     );
     m.add_party("Rent Co", &["landlord"]);
+    m.books_dir = Some(dir);
     m
 }