fix(cursor): use stdio ignore, sequential polling, move CursorConfig to types

- Change spawn stdio from piped to 'ignore' preventing buffer deadlock
- Replace setInterval with sequential setTimeout polling
- Fix TOCTOU in SIGKILL escalation (send directly without probing)
- Move CursorConfig interface to types.ts
- Change detectProvider default from 'openai' to 'unknown'
- Remove redundant removePidFile() when PID is null

tests/unit/cursor/cursor-models.test.ts

@@ -72,8 +72,8 @@ describe('detectProvider', () => {
     expect(detectProvider('cursor-small')).toBe('cursor');
   });
 
-  it('defaults to openai for unknown models', () => {
-    expect(detectProvider('unknown-model')).toBe('openai');
+  it('defaults to unknown for unrecognized models', () => {
+    expect(detectProvider('unknown-model')).toBe('unknown');
   });
 });