fix(lock): use recursive mkdir and add explicit existence check

- Changed mkdirSync to use recursive: true to create parent directories
- Added explicit existsSync check before mkdir since recursive mode doesn't throw EEXIST
- Updated test expectations to handle both error types from pRetry wrapping
- Fixed deeply nested path test to expect success with recursive mode

Author: jdalton

src/process-lock.ts

@@ -256,8 +256,13 @@ class ProcessLockManager {
             }
           }
 
-          // Atomic lock acquisition via mkdir.
-          mkdirSync(lockPath, { recursive: false })
+          // Check if lock already exists before creating.
+          if (existsSync(lockPath)) {
+            throw new Error(`Lock already exists: ${lockPath}`)
+          }
+
+          // Atomic lock acquisition via mkdir with recursive to create parent dirs.
+          mkdirSync(lockPath, { recursive: true })
 
           // Track lock for cleanup.
           this.activeLocks.add(lockPath)

test/process-lock.test.ts

@@ -49,7 +49,7 @@ describe.sequential('process-lock', () => {
       // Second acquire should fail
       await expect(
         processLock.acquire(testLockPath, { retries: 1, baseDelayMs: 10 }),
-      ).rejects.toThrow(/Lock already exists/)
+      ).rejects.toThrow(/Lock already exists|Failed to acquire lock/)
 
       release1()
     })
@@ -246,7 +246,7 @@ describe.sequential('process-lock', () => {
           baseDelayMs: 10,
           staleMs: 10_000,
         }),
-      ).rejects.toThrow(/Lock already exists/)
+      ).rejects.toThrow(/Lock already exists|Failed to acquire lock/)
 
       release()
     })
@@ -308,13 +308,11 @@ describe.sequential('process-lock', () => {
         'path',
       )
 
-      // Should work even with nested path
-      await expect(
-        processLock.acquire(deepPath, { retries: 1 }),
-      ).rejects.toThrow()
-
-      // mkdir with recursive: false should fail for non-existent parent
-      // This is expected behavior
+      // Should work with nested path (recursive: true creates parent dirs)
+      const release = await processLock.acquire(deepPath, { retries: 1 })
+      expect(existsSync(deepPath)).toBe(true)
+      release()
+      expect(existsSync(deepPath)).toBe(false)
     })
   })
 })